摄像头权限关闭后异常
描述：当app摄像头权限打开后，运行中的app和单例中的数据正常；切换到设置页面关闭摄像头权限后；再切换到app发生的变化
结果： activity会重新绘制，activity历史栈会保留，但是回退到历史栈的activity会重新从onCreate(***)开始；且单例中的数据被重置，例如：int 数据被重置为0，对象被重置为null
示例：
单例代码
public class CountManager {
private CountManager() {
}
public static CountManager getInstance() {
return SingleHolder.instance;
}
private static class SingleHolder {
private static final CountManager instance = new CountManager();
}
private int mCount = 0;
public void addCount() {
mCount++;
}
public int getCount() {
return mCount;
}
}
第一个activity
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity-1";
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
CountManager.getInstance().addCount(); //单例中数据增加
findViewById(R.id.btn_second_click).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this, SecondActivity.class));
}
});
Log.d(TAG, "onCreate: ");
}
@Override
protected void onResume() {
super.onResume();
Log.d(TAG, "onResume: " + CountManager.getInstance().getCount());
}
@Override
protected void onPause() {
super.onPause();
Log.d(TAG, "onPause: ");
}
@Override
protected void onDestroy() {
super.onDestroy();
Log.d(TAG, "onDestroy: ");
}
}
第二个activity
public class SecondActivity extends AppCompatActivity {
private static final String TAG = "MainActivity-Second";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
CountManager.getInstance().addCount();
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.replace(R.id.container, MainFragment.newInstance())
.commitNow();
}
Log.d(TAG, "onCreate: ");
}
@Override
protected void onResume() {
super.onResume();
Log.d(TAG, "onResume: "+ CountManager.getInstance().getCount());
}
@Override
protected void onPause() {
super.onPause();
Log.d(TAG, "onPause: ");
}
@Override
protected void onStop() {
super.onStop();
Log.d(TAG, "onStop: ");
}
@Override
protected void onDestroy() {
super.onDestroy();
Log.d(TAG, "onDestroy: ");
}
}
备注：记得app增加摄像头权限
运行结果
1、启动app后，在MainActivity，点击跳转到SecondActivity
D onCreate:
15:28:09.177 com.xiaoma.testc D onResume: 1
15:28:11.663 com.xiaoma.testc D onPause:
15:28:11.708 com.xiaoma.testc D onCreate:
15:28:11.751 com.xiaoma.testc D onResume: 2
2、切换到桌面，摄像头权限进行关闭操作或者打开后再关闭
15:31:44.956 com.xiaoma.testc D onPause:
15:31:44.989 com.xiaoma.testc D onStop:
---------------------------- PROCESS ENDED (31143) for package com.xiaoma.testc ----------------------------
可以看到进程关闭了的信息
3、再次点击app，查看里面的数据，然后进行回退历史栈
---------------------------- PROCESS STARTED (32348) for package com.xiaoma.testc ----------------------------
15:32:57.135 com.xiaoma.testc D onCreate:
15:32:57.170 com.xiaoma.testc D onResume: 1
15:33:13.688 com.xiaoma.testc D onPause:
//返回操作后
15:33:13.751 com.xiaoma.testc D onCreate:
15:33:13.755 com.xiaoma.testc D onResume: 2
15:33:14.162 com.xiaoma.testc D onStop:
15:33:14.167 com.xiaoma.testc D onDestroy:
可以看到重启启动了进程，且历史栈存在
总结
对于开发SDK的，由于需要宿主传递接口回调，会导致回调为null，所以在页面需要进行回调判断，进行相关的业务处理。