在Android中LayoutInflater的用途是什么?
当前回答
膨胀意味着读取描述布局(或GUI元素)的XML文件，并创建与之对应的实际对象，从而使对象在Android应用程序中可见。
final Dialog mDateTimeDialog = new Dialog(MainActivity.this);
// Inflate the root layout
final RelativeLayout mDateTimeDialogView = (RelativeLayout) getLayoutInflater().inflate(R.layout.date_time_dialog, null);
// Grab widget instance
final DateTimePicker mDateTimePicker = (DateTimePicker) mDateTimeDialogView.findViewById(R.id.DateTimePicker);
这个文件可以保存为date_time_dialog.xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/DateTimeDialog" android:layout_width="100px"
android:layout_height="wrap_content">
<com.dt.datetimepicker.DateTimePicker
android:id="@+id/DateTimePicker" android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<LinearLayout android:id="@+id/ControlButtons"
android:layout_width="fill_parent" android:layout_height="wrap_content"
android:layout_below="@+id/DateTimePicker"
android:padding="5dip">
<Button android:id="@+id/SetDateTime" android:layout_width="0dip"
android:text="@android:string/ok" android:layout_weight="1"
android:layout_height="wrap_content"
/>
<Button android:id="@+id/ResetDateTime" android:layout_width="0dip"
android:text="Reset" android:layout_weight="1"
android:layout_height="wrap_content"
/>
<Button android:id="@+id/CancelDialog" android:layout_width="0dip"
android:text="@android:string/cancel" android:layout_weight="1"
android:layout_height="wrap_content"
/>
</LinearLayout>
这个文件可以保存为date_time_picker.xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="wrap_content" `enter code here`
android:padding="5dip" android:id="@+id/DateTimePicker">
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:baselineAligned="true"
android:orientation="horizontal">
<LinearLayout
android:id="@+id/month_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="1dp"
android:layout_marginTop="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<Button
android:id="@+id/month_plus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_up_final"/>
<EditText
android:id="@+id/month_display"
android:layout_width="45dp"
android:layout_height="35dp"
android:background="@drawable/picker_middle"
android:focusable="false"
android:gravity="center"
android:singleLine="true"
android:textColor="#000000">
</EditText>
<Button
android:id="@+id/month_minus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_down_final"/>
</LinearLayout>
<LinearLayout
android:id="@+id/date_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="0.5dp"
android:layout_marginTop="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<Button
android:id="@+id/date_plus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_up_final"/>
<EditText
android:id="@+id/date_display"
android:layout_width="45dp"
android:layout_height="35dp"
android:background="@drawable/picker_middle"
android:gravity="center"
android:focusable="false"
android:inputType="number"
android:textColor="#000000"
android:singleLine="true"/>
<Button
android:id="@+id/date_minus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_down_final"/>
</LinearLayout>
<LinearLayout
android:id="@+id/year_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="0.5dp"
android:layout_marginTop="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<Button
android:id="@+id/year_plus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_up_final"/>
<EditText
android:id="@+id/year_display"
android:layout_width="45dp"
android:layout_height="35dp"
android:background="@drawable/picker_middle"
android:gravity="center"
android:focusable="false"
android:inputType="number"
android:textColor="#000000"
android:singleLine="true"/>
<Button
android:id="@+id/year_minus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_down_final"/>
</LinearLayout>
<LinearLayout
android:id="@+id/hour_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"
android:layout_marginTop="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<Button
android:id="@+id/hour_plus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_up_final"/>
<EditText
android:id="@+id/hour_display"
android:layout_width="45dp"
android:layout_height="35dp"
android:background="@drawable/picker_middle"
android:gravity="center"
android:focusable="false"
android:inputType="number"
android:textColor="#000000"
android:singleLine="true">
</EditText>
<Button
android:id="@+id/hour_minus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_down_final"/>
</LinearLayout>
<LinearLayout
android:id="@+id/min_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="0.35dp"
android:layout_marginTop="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<Button
android:id="@+id/min_plus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_up_final"/>
<EditText
android:id="@+id/min_display"
android:layout_width="45dp"
android:layout_height="35dp"
android:background="@drawable/picker_middle"
android:gravity="center"
android:focusable="false"
android:inputType="number"
android:textColor="#000000"
android:singleLine="true"/>
<Button
android:id="@+id/min_minus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_down_final"/>
</LinearLayout>
<LinearLayout
android:id="@+id/meridiem_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="0.35dp"
android:layout_marginTop="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<ToggleButton
android:id="@+id/toggle_display"
style="@style/SpecialToggleButton"
android:layout_width="40dp"
android:layout_height="32dp"
android:layout_marginLeft="5dp"
android:layout_marginTop="45dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:padding="5dp"
android:gravity="center"
android:textOn="@string/meridiem_AM"
android:textOff="@string/meridiem_PM"
android:checked="true"/>
<!-- android:checked="true" -->
</LinearLayout>
</LinearLayout>
</RelativeLayout>
MainActivity类保存为MainActivity.java:
public class MainActivity extends Activity {
EditText editText;
Button button_click;
public static Activity me = null;
String meridiem;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editText = (EditText)findViewById(R.id.edittext1);
button_click = (Button)findViewById(R.id.button1);
button_click.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view){
final Dialog mDateTimeDialog = new Dialog(MainActivity.this);
final RelativeLayout mDateTimeDialogView = (RelativeLayout) getLayoutInflater().inflate(R.layout.date_time_dialog, null);
final DateTimePicker mDateTimePicker = (DateTimePicker) mDateTimeDialogView.findViewById(R.id.DateTimePicker);
// mDateTimePicker.setDateChangedListener();
((Button) mDateTimeDialogView.findViewById(R.id.SetDateTime)).setOnClickListener(new OnClickListener() {
public void onClick(View v) {
mDateTimePicker.clearFocus();
int hour = mDateTimePicker.getHour();
String result_string = mDateTimePicker.getMonth() +" "+ String.valueOf(mDateTimePicker.getDay()) + ", " + String.valueOf(mDateTimePicker.getYear())
+ " " +(mDateTimePicker.getHour()<=9? String.valueOf("0"+mDateTimePicker.getHour()) : String.valueOf(mDateTimePicker.getHour())) + ":" + (mDateTimePicker.getMinute()<=9?String.valueOf("0"+mDateTimePicker.getMinute()):String.valueOf(mDateTimePicker.getMinute()))+" "+mDateTimePicker.getMeridiem();
editText.setText(result_string);
mDateTimeDialog.dismiss();
}
});
// Cancel the dialog when the "Cancel" button is clicked
((Button) mDateTimeDialogView.findViewById(R.id.CancelDialog)).setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
mDateTimeDialog.cancel();
}
});
// Reset Date and Time pickers when the "Reset" button is clicked
((Button) mDateTimeDialogView.findViewById(R.id.ResetDateTime)).setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
mDateTimePicker.reset();
}
});
// Setup TimePicker
// No title on the dialog window
mDateTimeDialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
// Set the dialog content view
mDateTimeDialog.setContentView(mDateTimeDialogView);
// Display the dialog
mDateTimeDialog.show();
}
});
}
}
其他回答
LayoutInflater类用于将布局XML文件的内容实例化到相应的View对象中。
换句话说，它接受一个XML文件作为输入，并从中构建View对象。
膨胀意味着读取描述布局(或GUI元素)的XML文件，并创建与之对应的实际对象，从而使对象在Android应用程序中可见。
final Dialog mDateTimeDialog = new Dialog(MainActivity.this);
// Inflate the root layout
final RelativeLayout mDateTimeDialogView = (RelativeLayout) getLayoutInflater().inflate(R.layout.date_time_dialog, null);
// Grab widget instance
final DateTimePicker mDateTimePicker = (DateTimePicker) mDateTimeDialogView.findViewById(R.id.DateTimePicker);
这个文件可以保存为date_time_dialog.xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/DateTimeDialog" android:layout_width="100px"
android:layout_height="wrap_content">
<com.dt.datetimepicker.DateTimePicker
android:id="@+id/DateTimePicker" android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<LinearLayout android:id="@+id/ControlButtons"
android:layout_width="fill_parent" android:layout_height="wrap_content"
android:layout_below="@+id/DateTimePicker"
android:padding="5dip">
<Button android:id="@+id/SetDateTime" android:layout_width="0dip"
android:text="@android:string/ok" android:layout_weight="1"
android:layout_height="wrap_content"
/>
<Button android:id="@+id/ResetDateTime" android:layout_width="0dip"
android:text="Reset" android:layout_weight="1"
android:layout_height="wrap_content"
/>
<Button android:id="@+id/CancelDialog" android:layout_width="0dip"
android:text="@android:string/cancel" android:layout_weight="1"
android:layout_height="wrap_content"
/>
</LinearLayout>
这个文件可以保存为date_time_picker.xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="wrap_content" `enter code here`
android:padding="5dip" android:id="@+id/DateTimePicker">
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:baselineAligned="true"
android:orientation="horizontal">
<LinearLayout
android:id="@+id/month_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="1dp"
android:layout_marginTop="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<Button
android:id="@+id/month_plus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_up_final"/>
<EditText
android:id="@+id/month_display"
android:layout_width="45dp"
android:layout_height="35dp"
android:background="@drawable/picker_middle"
android:focusable="false"
android:gravity="center"
android:singleLine="true"
android:textColor="#000000">
</EditText>
<Button
android:id="@+id/month_minus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_down_final"/>
</LinearLayout>
<LinearLayout
android:id="@+id/date_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="0.5dp"
android:layout_marginTop="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<Button
android:id="@+id/date_plus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_up_final"/>
<EditText
android:id="@+id/date_display"
android:layout_width="45dp"
android:layout_height="35dp"
android:background="@drawable/picker_middle"
android:gravity="center"
android:focusable="false"
android:inputType="number"
android:textColor="#000000"
android:singleLine="true"/>
<Button
android:id="@+id/date_minus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_down_final"/>
</LinearLayout>
<LinearLayout
android:id="@+id/year_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="0.5dp"
android:layout_marginTop="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<Button
android:id="@+id/year_plus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_up_final"/>
<EditText
android:id="@+id/year_display"
android:layout_width="45dp"
android:layout_height="35dp"
android:background="@drawable/picker_middle"
android:gravity="center"
android:focusable="false"
android:inputType="number"
android:textColor="#000000"
android:singleLine="true"/>
<Button
android:id="@+id/year_minus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_down_final"/>
</LinearLayout>
<LinearLayout
android:id="@+id/hour_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"
android:layout_marginTop="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<Button
android:id="@+id/hour_plus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_up_final"/>
<EditText
android:id="@+id/hour_display"
android:layout_width="45dp"
android:layout_height="35dp"
android:background="@drawable/picker_middle"
android:gravity="center"
android:focusable="false"
android:inputType="number"
android:textColor="#000000"
android:singleLine="true">
</EditText>
<Button
android:id="@+id/hour_minus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_down_final"/>
</LinearLayout>
<LinearLayout
android:id="@+id/min_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="0.35dp"
android:layout_marginTop="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<Button
android:id="@+id/min_plus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_up_final"/>
<EditText
android:id="@+id/min_display"
android:layout_width="45dp"
android:layout_height="35dp"
android:background="@drawable/picker_middle"
android:gravity="center"
android:focusable="false"
android:inputType="number"
android:textColor="#000000"
android:singleLine="true"/>
<Button
android:id="@+id/min_minus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_down_final"/>
</LinearLayout>
<LinearLayout
android:id="@+id/meridiem_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="0.35dp"
android:layout_marginTop="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<ToggleButton
android:id="@+id/toggle_display"
style="@style/SpecialToggleButton"
android:layout_width="40dp"
android:layout_height="32dp"
android:layout_marginLeft="5dp"
android:layout_marginTop="45dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:padding="5dp"
android:gravity="center"
android:textOn="@string/meridiem_AM"
android:textOff="@string/meridiem_PM"
android:checked="true"/>
<!-- android:checked="true" -->
</LinearLayout>
</LinearLayout>
</RelativeLayout>
MainActivity类保存为MainActivity.java:
public class MainActivity extends Activity {
EditText editText;
Button button_click;
public static Activity me = null;
String meridiem;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editText = (EditText)findViewById(R.id.edittext1);
button_click = (Button)findViewById(R.id.button1);
button_click.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view){
final Dialog mDateTimeDialog = new Dialog(MainActivity.this);
final RelativeLayout mDateTimeDialogView = (RelativeLayout) getLayoutInflater().inflate(R.layout.date_time_dialog, null);
final DateTimePicker mDateTimePicker = (DateTimePicker) mDateTimeDialogView.findViewById(R.id.DateTimePicker);
// mDateTimePicker.setDateChangedListener();
((Button) mDateTimeDialogView.findViewById(R.id.SetDateTime)).setOnClickListener(new OnClickListener() {
public void onClick(View v) {
mDateTimePicker.clearFocus();
int hour = mDateTimePicker.getHour();
String result_string = mDateTimePicker.getMonth() +" "+ String.valueOf(mDateTimePicker.getDay()) + ", " + String.valueOf(mDateTimePicker.getYear())
+ " " +(mDateTimePicker.getHour()<=9? String.valueOf("0"+mDateTimePicker.getHour()) : String.valueOf(mDateTimePicker.getHour())) + ":" + (mDateTimePicker.getMinute()<=9?String.valueOf("0"+mDateTimePicker.getMinute()):String.valueOf(mDateTimePicker.getMinute()))+" "+mDateTimePicker.getMeridiem();
editText.setText(result_string);
mDateTimeDialog.dismiss();
}
});
// Cancel the dialog when the "Cancel" button is clicked
((Button) mDateTimeDialogView.findViewById(R.id.CancelDialog)).setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
mDateTimeDialog.cancel();
}
});
// Reset Date and Time pickers when the "Reset" button is clicked
((Button) mDateTimeDialogView.findViewById(R.id.ResetDateTime)).setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
mDateTimePicker.reset();
}
});
// Setup TimePicker
// No title on the dialog window
mDateTimeDialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
// Set the dialog content view
mDateTimeDialog.setContentView(mDateTimeDialogView);
// Display the dialog
mDateTimeDialog.show();
}
});
}
}
下面是一个示例，用于获取布局的根视图的引用， 膨胀它并使用setContentView(视图视图)
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
LayoutInflater li=getLayoutInflater();
View rootView=li.inflate(R.layout.activity_main,null);
setContentView(rootView);
}
LayoutInflater是一个用于实例化布局XML文件到其相应的视图对象的类，可以在Java程序中使用。 简单来说，在android中有两种方法来创建UI。一种是静态的，另一种是动态的或程序化的。 假设我们有一个简单的布局main.xml，它有一个textview和一个edittext，如下所示。
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:id="@+id/layout1"
>
<TextView
android:id="@+id/namelabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Enter your name"
android:textAppearance="?android:attr/textAppearanceLarge" >
</TextView>
<EditText
android:id="@+id/name"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_marginTop="14dp"
android:ems="10">
</EditText>
</LinearLayout>
我们可以用静态的方式显示这个布局
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
创建视图的动态方式意味着在main.xml中没有提到视图，但我们希望在运行时显示视图。例如，我们在布局文件夹中有另一个XML文件footer.xml
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/TextView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:text="Add your record"
android:textSize="24sp" >
</TextView>
我们希望在主UI的运行时显示此文本框。这里我们将膨胀text。xml。看看:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
final LayoutInflater inflater = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
TextView t = (TextView)inflater.inflate(R.layout.footer,null);
lLayout = (LinearLayout)findViewById(R.id.layout1);
lLayout.addView(t);
这里我使用了getSystemService (String)来检索一个LayoutInflater实例。我可以使用getLayoutInflator()太膨胀，而不是使用getSystemService(字符串)如下所示:
LayoutInflator inflater = getLayoutInflater();
TextView t = (TextView) inflater.inflate(R.layout.footer, null);
lLayout.addView(t);
该类用于将布局XML文件实例化到相应的View对象中。永远不能直接使用它——使用getLayoutInflater()或getSystemService(String)来检索一个标准的LayoutInflater实例，该实例已经连接到当前上下文，并且为正在运行的设备正确配置了。例如:
LayoutInflater inflater = (LayoutInflater)context.getSystemService
(Context.LAYOUT_INFLATER_SERVICE);
参考:http://developer.android.com/reference/android/view/LayoutInflater.html
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