我正在使用 SurfaceView 在相机预览上进行绘制，改编本教程中的代码。该应用程序首先可以运行，然后在方向更改时崩溃，有时在第一次更改时崩溃，有时在更改两三次后崩溃。我见过很多类似的问题，但没有一个有解决方案（就我而言）。这是一个例外：
05-09 22:14:48.384: D/libEGL(829): loaded /vendor/lib/egl/libEGL_POWERVR_SGX540_120.so
05-09 22:14:48.400: D/libEGL(829): loaded /vendor/lib/egl/libGLESv1_CM_POWERVR_SGX540_120.so
05-09 22:14:48.408: D/libEGL(829): loaded /vendor/lib/egl/libGLESv2_POWERVR_SGX540_120.so
05-09 22:14:48.486: D/OpenGLRenderer(829): Enabling debug mode 0
05-09 22:14:49.056: I/Choreographer(829): Skipped 40 frames! The application may be doing too much work on its main thread.
05-09 22:14:49.337: D/dalvikvm(829): GC_FOR_ALLOC freed 113K, 2% free 8736K/8876K, paused 50ms, total 64ms
05-09 22:14:49.353: I/dalvikvm-heap(829): Grow heap (frag case) to 11.521MB for 3110416-byte allocation
[snip lots]
05-09 22:14:56.423: D/AndroidRuntime(829): Shutting down VM
05-09 22:14:56.423: W/dalvikvm(829): threadid=1: thread exiting with uncaught exception (group=0x4180a930)
05-09 22:14:56.439: E/AndroidRuntime(829): FATAL EXCEPTION: main
05-09 22:14:56.439: E/AndroidRuntime(829): java.lang.RuntimeException: Method called after release()
05-09 22:14:56.439: E/AndroidRuntime(829): at android.hardware.Camera.setHasPreviewCallback(Native Method)
05-09 22:14:56.439: E/AndroidRuntime(829): at android.hardware.Camera.access$600(Camera.java:131)
05-09 22:14:56.439: E/AndroidRuntime(829): at android.hardware.Camera$EventHandler.handleMessage(Camera.java:784)
05-09 22:14:56.439: E/AndroidRuntime(829): at android.os.Handler.dispatchMessage(Handler.java:99)
05-09 22:14:56.439: E/AndroidRuntime(829): at android.os.Looper.loop(Looper.java:137)
05-09 22:14:56.439: E/AndroidRuntime(829): at android.app.ActivityThread.main(ActivityThread.java:5041)
05-09 22:14:56.439: E/AndroidRuntime(829): at java.lang.reflect.Method.invokeNative(Native Method)
05-09 22:14:56.439: E/AndroidRuntime(829): at java.lang.reflect.Method.invoke(Method.java:511)
05-09 22:14:56.439: E/AndroidRuntime(829): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-09 22:14:56.439: E/AndroidRuntime(829): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-09 22:14:56.439: E/AndroidRuntime(829): at dalvik.system.NativeStart.main(Native Method)
05-09 22:14:58.236: I/Process(829): Sending signal. PID: 829 SIG: 9
我的主要活动包含相机预览：
public class MainActivity extends Activity implements SurfaceHolder.Callback, LocationListener {
private Camera camera;
private SurfaceView cameraSV;
private SurfaceHolder cameraSH;
private OverlayView overlay;
/* Activity event handlers */
// Called when activity is initialised by OS
@Override
public void onCreate(Bundle inst) {
super.onCreate(inst);
setContentView(R.layout.activity_main);
initCamera();
}
// Called when activity is closed by OS
@Override
public void onDestroy() {
super.onDestroy();
// Turn off the camera
stopCamera();
}
/* SurfaceHolder event handlers */
// Called when the surface is first created
public void surfaceCreated(SurfaceHolder holder) {
}
// Called when surface dimensions etc change
public void surfaceChanged(SurfaceHolder sh, int format, int width,
int height) {
// Start camera preview
startCamera(sh, width, height);
}
// Called when the surface is closed/destroyed
public void surfaceDestroyed(SurfaceHolder sh) {
stopCamera();
}
private void initCamera() {
cameraSV = (SurfaceView) findViewById(R.id.surface_camera);
cameraSH = cameraSV.getHolder();
cameraSH.addCallback(this);
camera = Camera.open();
overlay = (OverlayView) findViewById(R.id.surface_overlay);
overlay.getHolder().setFormat(PixelFormat.TRANSLUCENT);
overlay.setCamera(camera);
}
// Setup camera based on surface parameters
private void startCamera(SurfaceHolder sh, int width, int height) {
Camera.Parameters p = camera.getParameters();
for (Camera.Size s : p.getSupportedPreviewSizes()) {
p.setPreviewSize(s.width, s.height);
overlay.setPreviewSize(s);
break;
}
if (this.getResources().getConfiguration().orientation != Configuration.ORIENTATION_LANDSCAPE) {
// p.set("orientation", "portrait");
// p.setRotation(90);
camera.setDisplayOrientation(90);
} else {
// p.set("orientation", "landscape");
// p.setRotation(0);
camera.setDisplayOrientation(0);
}
camera.setParameters(p);
try {
camera.setPreviewDisplay(sh);
} catch (Exception e) { // Log surface setting exceptions
}
camera.startPreview();
}
// Stop camera when application ends
private void stopCamera() {
if (cameraSH != null) cameraSH.removeCallback(this);
if (camera != null) {
camera.stopPreview();
camera.release();
}
}
}
我的自定义 SurfaceView 类绘制在相机预览之上：
public class OverlayView extends SurfaceView {
private SurfaceHolder surfaceHolder;
private Camera camera;
private Camera.Size frameSize;
public OverlayView(Context ctx) {
super(ctx);
surfaceHolder= getHolder();
}
public OverlayView(Context ctx, AttributeSet attr) {
super(ctx, attr);
surfaceHolder = getHolder();
}
public void setPreviewSize(Camera.Size s) {
frameSize = s;
}
// Called by initCamera, to set callback
public void setCamera(Camera c) {
camera = c;
camera.setPreviewCallback(new PreviewCallback() {
// Called by camera hardware, with preview frame
public void onPreviewFrame(byte[] frame, Camera c) {
Canvas canvas = surfaceHolder.lockCanvas(null);
canvas.drawColor( 0, PorterDuff.Mode.CLEAR );
try {
// Perform overlay rendering here
Paint pt = new Paint();
pt.setColor(Color.BLACK);
pt.setTextSize(70);
canvas.drawText("Hi", 10, frameSize.height-10, pt);
} catch (Exception e) {
// Log/trap rendering errors
} finally {
surfaceHolder.unlockCanvasAndPost(canvas);
}
}
});
}
}
布局：
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<com.example.OverlayView android:id="@+id/surface_overlay"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
<SurfaceView android:id="@+id/surface_camera"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
</FrameLayout>
最后，我的清单具有以下权限：
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />