前言
源代码来自http://blog.csdn.net/xiaanming/article/details/10163203，由于不懂surfaceDestroyed的调用时机，网上一般都说在surfaceview隐藏的时候调用，但是按back键、按home键、锁屏、跳转到另一个非完全覆盖的activity是否会调用surfaceDestroyed，不是很清楚。 所以用打印日志的方式分析了下各个函数的执行调用过程。
很多surfaceview的demo中都用到了hasSurface，但是hasSurface又有什么作用呢？曾经深表怀疑，仔细分析过代码才明白
四种方式的日志
back
进入MipcaActivityCapture这个activity
01-09 16:59:51.118:E/MipcaActivityCapture(25152): onCreate
01-09 16:59:51.141:E/MipcaActivityCapture(25152): onResume
01-09 16:59:51.141:E/MipcaActivityCapture(25152): hasSurface=false
01-09 16:59:51.259:E/MipcaActivityCapture(25152): surfaceCreated
01-09 16:59:51.259:E/MipcaActivityCapture(25152): initCamera
点back
01-09 16:59:54.102:E/MipcaActivityCapture(25152): onPause
01-09 16:59:54.227:E/MipcaActivityCapture(25152): surfaceDestroyed
01-09 16:59:54.391:E/MipcaActivityCapture(25152): onStop
01-09 16:59:54.399:E/MipcaActivityCapture(25152): onDestroy
home
进入MipcaActivityCapture这个activity
01-09 16:59:51.118:E/MipcaActivityCapture(25152): onCreate
01-09 16:59:51.141:E/MipcaActivityCapture(25152): onResume
01-09 16:59:51.141:E/MipcaActivityCapture(25152): hasSurface=false
01-09 16:59:51.259:E/MipcaActivityCapture(25152): surfaceCreated
01-09 16:59:51.259:E/MipcaActivityCapture(25152): initCamera
点home
01-09 17:28:47.196:E/MipcaActivityCapture(26547): onPause
01-09 17:28:47.321:E/MipcaActivityCapture(26547): surfaceDestroyed
01-09 17:28:47.704:E/MipcaActivityCapture(26547): onStop
锁屏
进入MipcaActivityCapture这个activity
01-09 17:31:03.259:E/MipcaActivityCapture(26655): onCreate
01-09 17:31:03.282:E/MipcaActivityCapture(26655): hasSurface=false
01-09 17:31:03.282:E/MipcaActivityCapture(26655): onResume
01-09 17:31:03.438:E/MipcaActivityCapture(26655): surfaceCreated
01-09 17:31:03.438:E/MipcaActivityCapture(26655): initCamera
锁屏（按关机键）
01-09 17:31:09.907:E/MipcaActivityCapture(26655): onPause
01-09 17:31:09.938:E/MipcaActivityCapture(26655): onStop
解锁（按关机键）
01-09 17:35:51.509:E/MipcaActivityCapture(27383): onResume
01-09 17:35:51.509:E/MipcaActivityCapture(27383): hasSurface=true
01-09 17:35:51.509:E/MipcaActivityCapture(27383): initCamera
跳转到一个非完全覆盖的activity
进入MipcaActivityCapture这个activity
01-09 17:43:38.126:E/MipcaActivityCapture(27383): onCreate
01-09 17:43:38.165:E/MipcaActivityCapture(27383): onResume
01-09 17:43:38.165:E/MipcaActivityCapture(27383): hasSurface=false
01-09 17:43:38.251:E/MipcaActivityCapture(27383): surfaceCreated
01-09 17:43:38.251:E/MipcaActivityCapture(27383): initCamera
跳转到一个非完全覆盖的activity时
01-09 17:43:44.446:E/MipcaActivityCapture(27383): onPause
01-09 17:43:44.477: E/OtherActivity(27383):---------------onCreate--------------------
01-09 17:43:44.477: E/OtherActivity(27383):---------------onStart--------------------
01-09 17:43:44.477: E/OtherActivity(27383):---------------onResume--------------------
按back
01-09 17:43:50.954: E/OtherActivity(27383):---------------onPause--------------------
01-09 17:43:50.977:E/MipcaActivityCapture(27383): onResume
01-09 17:43:50.977: E/MipcaActivityCapture(27383):hasSurface=true
01-09 17:43:50.977:E/MipcaActivityCapture(27383): initCamera
01-09 17:43:51.954: E/OtherActivity(27383):---------------onStop--------------------
01-09 17:43:51.954: E/OtherActivity(27383):---------------onDestroy--------------------
总结
onPause会调用CameraManager.get().closeDriver();
surfaceCreated一般在OnResume之后调用，
按back或home都会调用surfaceDestroyed ，surfaceDestroyed在OnPause和OnStop之间调用。
但是锁屏不会调用surfaceDestroyed，解锁也不会调surfaceCreated
跳转到一个非完全覆盖的activity时也不会调surfaceDestroyed，返回时也不会调surfaceCreated
按back/home或者锁屏都会调用OnPause，导致CameraManager.get().closeDriver();所以下次进入activity的时候要initCamera，这是怎么实现的呢？看下面这段代码，展现了hasSurface的作用。
if(hasSurface) {
initCamera(surfaceHolder);
}else {
surfaceHolder.addCallback(this);
surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
锁屏解锁后hasSurface为true，调用initCamera。
按back或者home再回来时hasSurface为false，此时在onResume之后会调用surfaceCreated，在surfaceCreated里面会调用initCamera。
代码
稍微改了下原代码
在CODE上查看代码片
派生到我的代码片
package com.example.qr_codescan;
import java.io.IOException;
import java.util.Vector;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.Intent;
import android.content.res.AssetFileDescriptor;
import android.graphics.Bitmap;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnCompletionListener;
import android.os.Bundle;
import android.os.Handler;
import android.os.Vibrator;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceHolder.Callback;
import android.view.SurfaceView;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;
import com.google.zxing.BarcodeFormat;
import com.google.zxing.Result;
import com.mining.app.zxing.camera.CameraManager;
import com.mining.app.zxing.decoding.CaptureActivityHandler;
import com.mining.app.zxing.decoding.InactivityTimer;
import com.mining.app.zxing.view.ViewfinderView;
/**
* Initial the camera
* @author Ryan.Tang
*/
public class MipcaActivityCapture extends Activity implements Callback {
private static final String TAG = MipcaActivityCapture.class.getSimpleName();
private CaptureActivityHandler handler;
private ViewfinderView viewfinderView;
private boolean hasSurface;
private Vector<BarcodeFormat> decodeFormats;
private String characterSet;
private InactivityTimer inactivityTimer;
private MediaPlayer mediaPlayer;
private boolean playBeep;
private static final float BEEP_VOLUME = 0.10f;
private boolean vibrate;
Button btn;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
Log.e(TAG, "onCreate");
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_capture1);
//ViewUtil.addTopView(getApplicationContext(), this, R.string.scan_card);
CameraManager.init(getApplication());
viewfinderView = (ViewfinderView) findViewById(R.id.viewfinder_view);
Button mButtonBack = (Button) findViewById(R.id.button_back);
mButtonBack.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
MipcaActivityCapture.this.finish();
}
});
hasSurface = false;
inactivityTimer = new InactivityTimer(this);
btn=(Button) findViewById(R.id.btn1);
btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent intent=new Intent(MipcaActivityCapture.this, OtherActivity.class);
startActivity(intent);
}
});
}
@Override
protected void onResume() {
Log.e(TAG, "onResume");
super.onResume();
SurfaceView surfaceView = (SurfaceView) findViewById(R.id.preview_view);
SurfaceHolder surfaceHolder = surfaceView.getHolder();
Log.e(TAG, "hasSurface="+hasSurface);
if (hasSurface) {
initCamera(surfaceHolder);
} else {
surfaceHolder.addCallback(this);
surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
decodeFormats = null;
characterSet = null;
playBeep = true;
AudioManager audioService = (AudioManager) getSystemService(AUDIO_SERVICE);
if (audioService.getRingerMode() != AudioManager.RINGER_MODE_NORMAL) {
playBeep = false;
}
initBeepSound();
vibrate = true;
}
@Override
protected void onPause() {
super.onPause();
if (handler != null) {
handler.quitSynchronously();
handler = null;
}
CameraManager.get().closeDriver();
Log.e(TAG, "onPause");
}
@Override
protected void onStop() {
// TODO Auto-generated method stub
super.onStop();
Log.e(TAG, "onStop");
}
@Override
protected void onDestroy() {
inactivityTimer.shutdown();
super.onDestroy();
Log.e(TAG, "onDestroy");
}
/**
* 处理扫描结果
* @param result
* @param barcode
*/
public void handleDecode(Result result, Bitmap barcode) {
inactivityTimer.onActivity();
playBeepSoundAndVibrate();
String resultString = result.getText();
if (resultString.equals("")) {
Toast.makeText(MipcaActivityCapture.this, "Scan failed!", Toast.LENGTH_SHORT).show();
}else {
Intent resultIntent = new Intent();
Bundle bundle = new Bundle();
bundle.putString("result", resultString);
bundle.putParcelable("bitmap", barcode);
resultIntent.putExtras(bundle);
this.setResult(RESULT_OK, resultIntent);
}
MipcaActivityCapture.this.finish();
}
private void initCamera(SurfaceHolder surfaceHolder) {
Log.e(TAG, "initCamera");
try {
CameraManager.get().openDriver(surfaceHolder);
} catch (IOException ioe) {
return;
} catch (RuntimeException e) {
return;
}
if (handler == null) {
handler = new CaptureActivityHandler(this, decodeFormats,
characterSet);
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
Log.e(TAG, "surfaceCreated");
if (!hasSurface) {
hasSurface = true;
initCamera(holder);
}
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
hasSurface = false;
Log.e(TAG, "surfaceDestroyed");
}
public ViewfinderView getViewfinderView() {
return viewfinderView;
}
public Handler getHandler() {
return handler;
}
public void drawViewfinder() {
viewfinderView.drawViewfinder();
}
private void initBeepSound() {
if (playBeep && mediaPlayer == null) {
// The volume on STREAM_SYSTEM is not adjustable, and users found it
// too loud,
// so we now play on the music stream.
setVolumeControlStream(AudioManager.STREAM_MUSIC);
mediaPlayer = new MediaPlayer();
mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
mediaPlayer.setOnCompletionListener(beepListener);
AssetFileDescriptor file = getResources().openRawResourceFd(
R.raw.beep);
try {
mediaPlayer.setDataSource(file.getFileDescriptor(),
file.getStartOffset(), file.getLength());
file.close();
mediaPlayer.setVolume(BEEP_VOLUME, BEEP_VOLUME);
mediaPlayer.prepare();
} catch (IOException e) {
mediaPlayer = null;
}
}
}
private static final long VIBRATE_DURATION = 200L;
private void playBeepSoundAndVibrate() {
if (playBeep && mediaPlayer != null) {
mediaPlayer.start();
}
if (vibrate) {
Vibrator vibrator = (Vibrator) getSystemService(VIBRATOR_SERVICE);
vibrator.vibrate(VIBRATE_DURATION);
}
}
/**
* When the beep has finished playing, rewind to queue up another one.
*/
private final OnCompletionListener beepListener = new OnCompletionListener() {
public void onCompletion(MediaPlayer mediaPlayer) {
mediaPlayer.seekTo(0);
}
};
}
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