我想让我的应用看起来更专业,所以我决定添加一个启动画面。

我应该如何进行实现呢?


当前回答

以上所有的答案都非常好。但是存在内存泄漏的问题。 这个问题在Android社区通常被称为“泄露活动”。这到底是什么意思呢?

当配置发生变化时,比如方向变化,Android会销毁Activity并重新创建它。通常,垃圾收集器只会清除旧Activity实例的已分配内存,一切正常。

“泄漏一个活动”指的是垃圾收集器无法清除旧活动实例的已分配内存的情况,因为它被(强)引用于一个活动实例外的对象。每个Android应用程序都分配了特定数量的内存。当垃圾回收器不能释放未使用的内存时,应用程序的性能将逐渐下降,最终崩溃并出现OutOfMemory错误。

如何确定应用程序是否泄漏内存?最快的方法是在Android Studio中打开内存选项卡,并在改变方向时注意分配的内存。 如果分配的内存一直在增加而不减少,那么就有内存泄漏。

1.当用户改变方向时内存泄漏。

首先,你需要在布局资源splashscreen.xml文件中定义启动画面

启动画面活动的示例代码。

public class Splash extends Activity {
 // 1. Create a static nested class that extends Runnable to start the main Activity
    private static class StartMainActivityRunnable implements Runnable {
        // 2. Make sure we keep the source Activity as a WeakReference (more on that later)
        private WeakReference mActivity;

        private StartMainActivityRunnable(Activity activity) {
         mActivity = new WeakReference(activity);
        }

        @Override
        public void run() {
         // 3. Check that the reference is valid and execute the code
            if (mActivity.get() != null) {
             Activity activity = mActivity.get();
             Intent mainIntent = new Intent(activity, MainActivity.class);
             activity.startActivity(mainIntent);
             activity.finish();
            }
        }
    }

    /** Duration of wait **/
    private final int SPLASH_DISPLAY_LENGTH = 1000;

    // 4. Declare the Handler as a member variable
    private Handler mHandler = new Handler();

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(icicle);
        setContentView(R.layout.splashscreen);

        // 5. Pass a new instance of StartMainActivityRunnable with reference to 'this'.
        mHandler.postDelayed(new StartMainActivityRunnable(this), SPLASH_DISPLAY_LENGTH);
    }

    // 6. Override onDestroy()
    @Override
    public void onDestroy() {
     // 7. Remove any delayed Runnable(s) and prevent them from executing.
     mHandler.removeCallbacksAndMessages(null);

     // 8. Eagerly clear mHandler allocated memory
     mHandler = null;
    }
}

欲了解更多信息,请点击此链接

其他回答

以上所有的答案都非常好。但是存在内存泄漏的问题。 这个问题在Android社区通常被称为“泄露活动”。这到底是什么意思呢?

当配置发生变化时,比如方向变化,Android会销毁Activity并重新创建它。通常,垃圾收集器只会清除旧Activity实例的已分配内存,一切正常。

“泄漏一个活动”指的是垃圾收集器无法清除旧活动实例的已分配内存的情况,因为它被(强)引用于一个活动实例外的对象。每个Android应用程序都分配了特定数量的内存。当垃圾回收器不能释放未使用的内存时,应用程序的性能将逐渐下降,最终崩溃并出现OutOfMemory错误。

如何确定应用程序是否泄漏内存?最快的方法是在Android Studio中打开内存选项卡,并在改变方向时注意分配的内存。 如果分配的内存一直在增加而不减少,那么就有内存泄漏。

1.当用户改变方向时内存泄漏。

首先,你需要在布局资源splashscreen.xml文件中定义启动画面

启动画面活动的示例代码。

public class Splash extends Activity {
 // 1. Create a static nested class that extends Runnable to start the main Activity
    private static class StartMainActivityRunnable implements Runnable {
        // 2. Make sure we keep the source Activity as a WeakReference (more on that later)
        private WeakReference mActivity;

        private StartMainActivityRunnable(Activity activity) {
         mActivity = new WeakReference(activity);
        }

        @Override
        public void run() {
         // 3. Check that the reference is valid and execute the code
            if (mActivity.get() != null) {
             Activity activity = mActivity.get();
             Intent mainIntent = new Intent(activity, MainActivity.class);
             activity.startActivity(mainIntent);
             activity.finish();
            }
        }
    }

    /** Duration of wait **/
    private final int SPLASH_DISPLAY_LENGTH = 1000;

    // 4. Declare the Handler as a member variable
    private Handler mHandler = new Handler();

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(icicle);
        setContentView(R.layout.splashscreen);

        // 5. Pass a new instance of StartMainActivityRunnable with reference to 'this'.
        mHandler.postDelayed(new StartMainActivityRunnable(this), SPLASH_DISPLAY_LENGTH);
    }

    // 6. Override onDestroy()
    @Override
    public void onDestroy() {
     // 7. Remove any delayed Runnable(s) and prevent them from executing.
     mHandler.removeCallbacksAndMessages(null);

     // 8. Eagerly clear mHandler allocated memory
     mHandler = null;
    }
}

欲了解更多信息,请点击此链接

这是完整的代码

SplashActivity.java

public class SplashActivity extends AppCompatActivity {

private final int SPLASH_DISPLAY_DURATION = 1000;

@Override
public void onCreate(Bundle bundle) {
    super.onCreate(bundle);


    new Handler().postDelayed(new Runnable(){
        @Override
        public void run() {

            Intent mainIntent = new Intent(SplashActivity.this,MainActivity.class);
            SplashActivity.this.startActivity(mainIntent);
            SplashActivity.this.finish();
        }
    }, SPLASH_DISPLAY_DURATION);
}}

在drawables中创建bg_splash.xml

<?xml version="1.0" encoding="utf-8"?><layer-list xmlns:android="http://schemas.android.com/apk/res/android">

<item
    android:drawable="@color/app_color"/>

<item>
    <bitmap
        android:gravity="center"
        android:src="@drawable/ic_in_app_logo_big"/>
</item></layer-list>

在styles.xml中创建一个自定义主题

<style name="SplashTheme" parent="Theme.AppCompat.NoActionBar">
    <item name="android:windowBackground">@drawable/bg_splash</item>
</style>

最后在AndroidManifest.xml中指定活动的主题

<activity
        android:name=".activities.SplashActivity"
        android:label="@string/app_name"
        android:screenOrientation="portrait"
        android:theme="@style/SplashTheme">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

欢呼。

一个超级灵活的启动屏幕如何,可以使用相同的代码,并在AndroidManifest.xml中定义,因此代码永远不需要更改。我通常开发代码库,不喜欢定制代码,因为它很草率。

<activity
        android:name=".SplashActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
        <meta-data android:name="launch_class" android:value="com.mypackage.MyFirstActivity" />
        <meta-data android:name="duration" android:value="5000" />
</activity>

然后SpashActivity本身查找“launch_class”的元数据,然后创建Intent本身。元数据“持续时间”定义了启动画面持续的时间。

public class SplashActivity extends Activity {

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle icicle) {
    super.onCreate(icicle);
    setContentView(R.layout.activity_splash);

    ComponentName componentName = new ComponentName(this, this.getClass());

    try {
        Bundle bundle = null;
        bundle = getPackageManager().getActivityInfo(componentName, PackageManager.GET_META_DATA).metaData;
        String launch_class = bundle.getString("launch_class");
        //default of 2 seconds, otherwise defined in manifest
        int duration = bundle.getInt("duration", 2000);

        if(launch_class != null) {
            try {
                final Class<?> c = Class.forName(launch_class);

                new Handler().postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        Intent intent = new Intent(SplashActivity.this, c);
                        startActivity(intent);
                        finish();
                    }
                }, duration);

            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }
        }
    } catch (PackageManager.NameNotFoundException e) {
        e.printStackTrace();
    }
  }
}

Create an activity: Splash Create a layout XML file: splash.xml Put UI components in the splash.xml layout so it looks how you want your Splash.java may look like this: public class Splash extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.splash); int secondsDelayed = 1; new Handler().postDelayed(new Runnable() { public void run() { startActivity(new Intent(Splash.this, ActivityB.class)); finish(); } }, secondsDelayed * 1000); } } change ActivityB.class to whichever activity you want to start after the splash screen check your manifest file and it should look like

<活动 android: name = "。屏” android: label = " @string / app_name " > > < /活动 <活动 android: name = "。飞溅” android: label = " @string / title_activity_splash_screen " > <意图过滤器> <action android:name="android.intent.action. main " /> <category android:name="android.intent.category. launcher " /> < /意图过滤器> > < /活动

在我的例子中,我不想创建一个新的活动只是为了显示2秒的图像。当启动我的MainActivity,图像被加载到持有者使用毕加索,我知道这需要大约1秒的加载,所以我决定做以下在我的MainActivity OnCreate:

splashImage = (ImageView) findViewById(R.id.spllll);

    this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);

    int secondsDelayed = 1;
    new Handler().postDelayed(new Runnable() {
        public void run() {
            getWindow().clearFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
            splashImage.setVisibility(View.GONE);

        }
    }, secondsDelayed * 2000);

当启动应用程序时,发生的第一件事是显示ImageView,并通过将窗口标志设置为全屏来删除状态栏。然后我使用Handler运行2秒,2秒后我清除全屏标志,并设置ImageView的可见性为GONE。简单,简单,有效。