windowIsTranslucent和windowBackground对比
在Activity A切换到Activity B时,有时会遇到黑屏或者白屏的闪屏问题,经常我们会给Activity B设置一个透明主题来解决,即通过设置属性android:windowIsTranslucent=true或者android:windowBackground=@color/transparent。那么这两个属性有区别呢?下面从它们对Activity生命周期的影响来对比说明。
android:windowIsTranslucent 窗口是否设置为半透明
android:windowBackground 整个窗口的背景,包括边框和内部
Activity A :MainActivity.java
public class MainActivity extends AppCompatActivity implements View.OnClickListener{ private Button btnTransActivity; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Log.e(Contants.TAG,"MainActivity onCreate"); setContentView(R.layout.activity_main); initView(); initListener(); } @Override protected void onRestart() { super.onRestart(); Log.e(Contants.TAG,"MainActivity onRestart"); } @Override protected void onStart() { super.onStart(); Log.e(Contants.TAG,"MainActivity onStart"); } @Override protected void onResume() { super.onResume(); Log.e(Contants.TAG,"MainActivity onResume"); } @Override protected void onPause() { super.onPause(); Log.e(Contants.TAG,"MainActivity onPause"); } @Override protected void onStop() { super.onStop(); Log.e(Contants.TAG,"MainActivity onStop"); } @Override protected void onDestroy() { super.onDestroy(); Log.e(Contants.TAG,"MainActivity onDestroy"); } private void initView() { btnTransActivity = findViewById(R.id.btnTransActivity); } private void initListener() { btnTransActivity.setOnClickListener(this); } @Override public void onClick(View v) { switch (v.getId()){ case R.id.btnTransActivity: Intent intent = new Intent(MainActivity.this,TransparentThemeActivity.class); startActivity(intent); break; default: break; } }}
Activity B:TransparentThemeActivity
public class TransparentThemeActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Log.e(Contants.TAG,"TransparentThemeActivity onCreate"); setContentView(R.layout.activity_transparent_theme); } @Override protected void onRestart() { super.onRestart(); Log.e(Contants.TAG,"TransparentThemeActivity onRestart"); } @Override protected void onStart() { super.onStart(); Log.e(Contants.TAG,"TransparentThemeActivity onStart"); } @Override protected void onResume() { super.onResume(); Log.e(Contants.TAG,"TransparentThemeActivity onResume"); } @Override protected void onPause() { super.onPause(); Log.e(Contants.TAG,"TransparentThemeActivity onPause"); } @Override protected void onStop() { super.onStop(); Log.e(Contants.TAG,"TransparentThemeActivity onStop"); } @Override protected void onDestroy() { super.onDestroy(); Log.e(Contants.TAG,"TransparentThemeActivity onDestroy"); }}
Activity B的theme
后台可见状态:onStart
用户可见状态:onResume
1、Activit A切换到B
(1)android:windowIsTranslucent = true
07-01 17:22:42.768 13454-13454/com.lmz.viewdemo E/activity: MainActivity onCreate07-01 17:22:42.836 13454-13454/com.lmz.viewdemo E/activity: MainActivity onStart07-01 17:22:42.839 13454-13454/com.lmz.viewdemo E/activity: MainActivity onResume07-01 17:22:48.925 13454-13454/com.lmz.viewdemo E/activity: MainActivity onPause07-01 17:22:48.953 13454-13454/com.lmz.viewdemo E/activity: TransparentThemeActivity onCreate07-01 17:22:48.975 13454-13454/com.lmz.viewdemo E/activity: TransparentThemeActivity onStart07-01 17:22:48.979 13454-13454/com.lmz.viewdemo E/activity: TransparentThemeActivity onResume
从打印的log中可以发现Activity A(MainActivity)切换到B时,只执行到了onPause方法,并没有执行onStop方法,所以在Activity B对用户可见时,下面的Activity A是处于部分可见的状态。
(2)android:windowBackground=@color/transparent
07-01 18:33:26.480 15730-15730/com.lmz.viewdemo E/activity: MainActivity onCreate07-01 18:33:26.542 15730-15730/com.lmz.viewdemo E/activity: MainActivity onStart07-01 18:33:26.544 15730-15730/com.lmz.viewdemo E/activity: MainActivity onResume07-01 18:33:43.268 15730-15730/com.lmz.viewdemo E/activity: MainActivity onPause07-01 18:33:43.294 15730-15730/com.lmz.viewdemo E/activity: TransparentThemeActivity onCreate07-01 18:33:43.312 15730-15730/com.lmz.viewdemo E/activity: TransparentThemeActivity onStart07-01 18:33:43.315 15730-15730/com.lmz.viewdemo E/activity: TransparentThemeActivity onResume07-01 18:33:43.698 15730-15730/com.lmz.viewdemo E/activity: MainActivity onStop
activity A和B的生命周期执行顺序正常。
2、在Activity B页面,点击back键返回到A页面
(1)android:windowIsTranslucent = true
07-01 18:44:22.894 16995-16995/com.lmz.viewdemo E/activity: TransparentThemeActivity onPause07-01 18:44:22.907 16995-16995/com.lmz.viewdemo E/activity: MainActivity onResume07-01 18:44:22.935 16995-16995/com.lmz.viewdemo E/activity: TransparentThemeActivity onStop07-01 18:44:22.936 16995-16995/com.lmz.viewdemo E/activity: TransparentThemeActivity onDestroy
从1的activity切换操作中可知Activity A(MainActivity)并未调用onStop方法,只调用了onPause,所以点击back键,Activity A要从onPause状态到对用户可见,只需要调用onResume方法(可上google官网查看activity生命周期图)。
(2)android:windowBackground=@color/transparent
07-01 18:42:34.013 15730-15730/com.lmz.viewdemo E/activity: TransparentThemeActivity onPause07-01 18:42:34.019 15730-15730/com.lmz.viewdemo E/activity: MainActivity onRestart07-01 18:42:34.019 15730-15730/com.lmz.viewdemo E/activity: MainActivity onStart07-01 18:42:34.020 15730-15730/com.lmz.viewdemo E/activity: MainActivity onResume07-01 18:42:34.329 15730-15730/com.lmz.viewdemo E/activity: TransparentThemeActivity onStop07-01 18:42:34.329 15730-15730/com.lmz.viewdemo E/activity: TransparentThemeActivity onDestroy
点击back键,Activity A从onStop状态到用户可见状态,需要调用onRestart、onStart、onResume方法,所以,点击back键也不会影响到activity的生命周期
3、停留在B页面,将应用从前台切到后台
(1)android:windowIsTranslucent = true
07-01 18:48:51.428 16995-16995/com.lmz.viewdemo E/activity: TransparentThemeActivity onPause07-01 18:48:51.483 16995-16995/com.lmz.viewdemo E/activity: MainActivity onStop07-01 18:48:51.486 16995-16995/com.lmz.viewdemo E/activity: TransparentThemeActivity onStop
从日志中可以看到,Activity A和Activity B都完全不可见(onStop)。而在A切到B时,A只调用了onPause方法,所以切到后台时,A到完全不可见,也调用onStop方法。
(2)android:windowBackground=@color/transparent
07-01 18:51:15.099 18093-18093/com.lmz.viewdemo E/activity: TransparentThemeActivity onPause07-01 18:51:15.151 18093-18093/com.lmz.viewdemo E/activity: TransparentThemeActivity onStop
在A切换到B时,A已经完全不可见了,所以切到后台时,只有Activity B从可见到完全不可见,会调用onPause、onStop方法。
4、将应用切回前台
(1)android:windowIsTranslucent = true
07-01 18:49:19.897 16995-16995/com.lmz.viewdemo E/activity: MainActivity onRestart07-01 18:49:19.901 16995-16995/com.lmz.viewdemo E/activity: MainActivity onStart07-01 18:49:19.904 16995-16995/com.lmz.viewdemo E/activity: TransparentThemeActivity onRestart07-01 18:49:19.906 16995-16995/com.lmz.viewdemo E/activity: TransparentThemeActivity onStart07-01 18:49:19.907 16995-16995/com.lmz.viewdemo E/activity: TransparentThemeActivity onResume
从日志中可以看到,Activity A和B都从不可见状态(onStop)到可见的状态,只有B是到用户可见状态(onResume)。
(2)android:windowBackground=@color/transparent
07-01 18:51:40.964 18093-18093/com.lmz.viewdemo E/activity: TransparentThemeActivity onRestart07-01 18:51:40.964 18093-18093/com.lmz.viewdemo E/activity: TransparentThemeActivity onStart07-01 18:51:40.965 18093-18093/com.lmz.viewdemo E/activity: TransparentThemeActivity onResume
只有activity B从不可见状态到用户可见的状态。
小结:
1、android:windowBackground不影响Activity的生命周期,即启动设置了该属性的Activity的生命周期不会受到影响。
2、android:windowIsTranslucent = true会影响到Activity的生命周期,比如启动一个设置了该属性的Activity,若该activity对用户可见时,启动它的activity(即它下层的activity)并未完全不可见(即调用到了onPause,不会调用onStop方法),具体可见上面的操作对Activity生命周期的影响。
优化:在实际开发中,发现对于Activity切换出现黑屏或者白屏处理中,若使用android:windowBackground对于7.0系统以上的手机还是会有闪屏的现象,若使用android:windowIsTranslucent = true就不会有闪屏现象,但是有两种情况需要进行优化:
1、需要在应用从前台切到后台时,执行操作。
判断是否切换后台的时机就需要放到onPause中去,若是切换后台,则执行操作。
2、需要在应用从后台切到前台时,执行操作。
若Activity A的上一层Activity B是透明主题,并且当前Activity B对用户完全可见的,此时Activity A处于onPause状态。
(1)停留在Activity B页面,应用从前台切换到后台时,Activity A也会执行onStop方法, 在onStop方法中判断应用是否切换到后台,是,将全局变量AppUtils.isBackGroundStart置为true,否则置为false。
(2)应用从后台切回前台时,当前只会有一个Activity会执行onResume方法(停留在Activity B页面时切到后台,所以切回前台时,只有Activity B会执行onResume), 此时可以通过全局变量isBackGroundStart判断应用是否是从后台切到前台的,执行需要在这个时机完成的操作后将isBackGroundStart置为false。
AppUtils.java
public static boolean isBackGroundStart = false;//是否从后台开启 /** * * 若Activity A的上一层Activity B是透明主题,并且当前Activity B对用户完全可见的,此时Activity A处于onPause状态。 * 1、停留在Activity B页面,应用从前台切换到后台时,Activity A也会执行onStop方法, * 在onStop方法中判断应用是否切换到后台,是,将全局变量AppUtils.isBackGroundStart置为true,否则置为false。 * 2、应用从后台切回前台时,当前只会有一个Activity会执行onResume方法(停留在Activity B页面时切到后台,所以切回前台时,只有Activity B会执行onResume), * 此时可以通过全局变量isBackGroundStart判断应用是否是从后台切到前台的,执行需要在这个时机完成的操作后将isBackGroundStart置为false。 * !!!注意:这里的透明主题是指使用android:windowIsTranslucent = true设置窗口半透明 * @param context * @return */ public static boolean isBackground(Context context) { ActivityManager ActivityManager = (ActivityManager) context .getSystemService(ACTIVITY_SERVICE); List appProcesses = ActivityManager .getRunningAppProcesses(); isBackGroundStart = false; if (TextUtil.isValidate(appProcesses)) { for (android.app.ActivityManager.RunningAppProcessInfo appProcess : appProcesses) { if (appProcess != null && appProcess.processName.equals(context.getPackageName())) { /* BACKGROUND=400 EMPTY=500 FOREGROUND=100 GONE=1000 PERCEPTIBLE=130 SERVICE=300 ISIBLE=200 */ if (appProcess.importance != android.app.ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND) { //后台 isBackGroundStart = true; return true; } else { //前台 return false; } } } } return false; }
ActivityA.java
public class ActivityA extends AppCompatActivity{ @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_a); } @Override protected void onResume() { super.onResume(); if (AppUtils.isBackGroundStart){ //TODO 执行操作 AppUtils.isBackGroundStart = false; } } @Override protected void onPause() { super.onPause(); } @Override protected void onStop() { super.onStop(); AppUtils.isBackground(ActivityA.this); }}
ActivityB.java
public class ActivityB extends AppCompatActivity{ @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_b); } @Override protected void onResume() { super.onResume(); if (AppUtils.isBackGroundStart){ //TODO 执行操作 AppUtils.isBackGroundStart = false; } } @Override protected void onPause() { super.onPause(); } @Override protected void onStop() { super.onStop(); AppUtils.isBackground(ActivityB.this); }}
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