在Twitter(官方应用)等Android应用中,当你遇到一个ListView时,你可以下拉它(它会在发布时反弹)来刷新内容。
我想知道,在你看来,最好的实现方式是什么?
我能想到的一些可能性:
一个在ListView顶部的项目-然而我不认为滚动回项目位置1(基于0)在ListView上的动画是一个简单的任务。
ListView之外的另一个视图-但我需要注意在它被拉时将ListView位置向下移动,我不确定我们是否可以检测到对ListView的拖动触摸是否仍然真正滚动ListView上的项。
你有什么推荐吗?
另外,我想知道官方的Twitter应用程序源代码什么时候发布。有消息说它会发布,但6个月过去了,我们一直没有听到它的消息。
我有很简单的方法来做到这一点,但现在肯定是万无一失的方法
这是我的代码
PullDownListView.java
package com.myproject.widgets;
import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ListView;
/**
* @author Pushpan
* @date Nov 27, 2012
**/
public class PullDownListView extends ListView implements OnScrollListener {
private ListViewTouchEventListener mTouchListener;
private boolean pulledDown;
public PullDownListView(Context context) {
super(context);
init();
}
public PullDownListView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public PullDownListView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init();
}
private void init() {
setOnScrollListener(this);
}
private float lastY;
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
lastY = ev.getRawY();
} else if (ev.getAction() == MotionEvent.ACTION_MOVE) {
float newY = ev.getRawY();
setPulledDown((newY - lastY) > 0);
postDelayed(new Runnable() {
@Override
public void run() {
if (isPulledDown()) {
if (mTouchListener != null) {
mTouchListener.onListViewPulledDown();
setPulledDown(false);
}
}
}
}, 400);
lastY = newY;
} else if (ev.getAction() == MotionEvent.ACTION_UP) {
lastY = 0;
}
return super.dispatchTouchEvent(ev);
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
setPulledDown(false);
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
}
public interface ListViewTouchEventListener {
public void onListViewPulledDown();
}
public void setListViewTouchListener(
ListViewTouchEventListener touchListener) {
this.mTouchListener = touchListener;
}
public ListViewTouchEventListener getListViewTouchListener() {
return mTouchListener;
}
public boolean isPulledDown() {
return pulledDown;
}
public void setPulledDown(boolean pulledDown) {
this.pulledDown = pulledDown;
}
}
你只需要在你的活动上实现ListViewTouchEventListener,你想使用这个ListView并设置监听器
我在PullDownListViewActivity中实现了它
package com.myproject.activities;
import android.app.Activity;
import android.os.Bundle;
/**
* @author Pushpan
*
*/
public class PullDownListViewActivity extends Activity implements ListViewTouchEventListener {
private PullDownListView listView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
listView = new PullDownListView(this);
setContentView(listView);
listView.setListViewTouchListener(this);
//setItems in listview
}
public void onListViewPulledDown(){
Log.("PullDownListViewActivity", "ListView pulled down");
}
}
这对我很有用:)
那些正在寻找实现拉刷新功能的RecyclerView可以遵循我的简单教程如何实现拉刷新的RecyclerView在Android。
要导入的库
implementation 'androidx.appcompat:appcompat:1.2.0'
implementation 'androidx.gridlayout:gridlayout:1.0.0'
XML代码
<androidx.swiperefreshlayout.widget.SwipeRefreshLayout
android:id="@+id/swipe_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</androidx.swiperefreshlayout.widget.SwipeRefreshLayout>
活动JAVA代码
import androidx.appcompat.app.AppCompatActivity;
import androidx.swiperefreshlayout.widget.SwipeRefreshLayout;
import android.os.Bundle;
import android.os.Handler;
public class MainActivity extends AppCompatActivity {
private SwipeRefreshLayout swipeRefreshLayout;
...
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
...
swipeRefreshLayout = findViewById(R.id.swipe_layout);
initializeRefreshListener();
}
void initializeRefreshListener() {
swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
@Override
public void onRefresh() {
// This method gets called when user pull for refresh,
// You can make your API call here,
// We are using adding a delay for the moment
final Handler handler = new Handler();
handler.postDelayed(new Runnable() {
@Override
public void run() {
if(swipeRefreshLayout.isRefreshing()) {
swipeRefreshLayout.setRefreshing(false);
}
}
}, 3000);
}
});
}
最后,谷歌发布了一个官方版本的拉取刷新库!
它被称为swiperfreshlayout,在支持库中,文档在这里:
Add SwipeRefreshLayout as a parent of view which will be treated as a pull to refresh the layout. (I took ListView as an example, it can be any View like LinearLayout, ScrollView etc.)
<androidx.swiperefreshlayout.widget.SwipeRefreshLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/pullToRefresh"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ListView
android:id="@+id/listView"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</androidx.swiperefreshlayout.widget.SwipeRefreshLayout>
Add a listener to your class
protected void onCreate(Bundle savedInstanceState) {
final SwipeRefreshLayout pullToRefresh = findViewById(R.id.pullToRefresh);
pullToRefresh.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
@Override
public void onRefresh() {
refreshData(); // your code
pullToRefresh.setRefreshing(false);
}
});
}
你也可以调用pullToRefresh.setRefreshing(true/false);按您的要求。
更新
Android支持库已弃用,并已被AndroidX所取代。新库的链接可以在这里找到。
此外,你需要添加以下依赖到你的项目:
implementation 'androidx.swiperefreshlayout:swiperefreshlayout:1.1.0'
OR
你可以去Refactor>>Migrate to AndroidX, Android Studio会为你处理依赖项。