在我的应用程序中，我使用ViewPager. 我创建了几个空白页。在页面预览ViewPager上放置相机，如 development.android.com 中所述。但是当我尝试运行应用程序时它失败了。如何解决这个问题呢 ？
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
private SurfaceHolder mHolder;
private Camera mCamera;
public CameraPreview(Context context, Camera camera) {
super(context);
mCamera = camera;
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = getHolder();
mHolder.addCallback(this);
// deprecated setting, but required on Android versions prior to 3.0
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, now tell the camera where to draw the preview.
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
} catch (IOException e) {
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// empty. Take care of releasing the Camera preview in your activity.
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// If your preview can change or rotate, take care of those events here.
// Make sure to stop the preview before resizing or reformatting it.
if (mHolder.getSurface() == null){
// preview surface does not exist
return;
}
// stop preview before making changes
try {
mCamera.stopPreview();
} catch (Exception e){
// ignore: tried to stop a non-existent preview
}
// set preview size and make any resize, rotate or
// reformatting changes here
// start preview with new settings
try {
mCamera.setPreviewDisplay(mHolder);
mCamera.startPreview();
} catch (Exception e){
}
}
}
主要活动：
public class CamActivity extends Activity {
private List<View> mPages;
private View mPage1;
private View mPage2;
private View mPage3;
private Camera mCamera;
private CameraPreview mPreview;
private FrameLayout preview;
private ViewPager mPager;
private TitlePageIndicator mTitleIndicator;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
initUi();
mCamera = getCameraInstance();
mPreview = new CameraPreview(this, mCamera);
}
public static Camera getCameraInstance(){
Camera c = null;
try {
c = Camera.open(); // attempt to get a Camera instance
}
catch (Exception e){
// Camera is not available (in use or does not exist)
}
return c; // returns null if camera is unavailable
}
private void initUi() {
LayoutInflater inflater = LayoutInflater.from(this);
mPages = new ArrayList<View>();
mPage1 = inflater.inflate(R.layout.page1, null);
mPage1.setTag(getString(R.string.capture));
mPage2 = inflater.inflate(R.layout.page2, null);
mPage2.setTag(getString(R.string.text2));
mPage3 = inflater.inflate(R.layout.page3, null);
mPage3.setTag(getString(R.string.text3));
mPages.add(mPage1);
mPages.add(mPage2);
mPages.add(mPage3);
MainPageAdapter adapter = new MainPageAdapter(mPages);
mPager = (ViewPager) findViewById(R.id.viewpager);
mPager.setAdapter(adapter);
mPager.setCurrentItem(0);
mTitleIndicator = (TitlePageIndicator) findViewById(R.id.indicator);
mTitleIndicator.setViewPager(mPager);
mTitleIndicator.setCurrentItem(0);
mTitleIndicator.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
public void onPageSelected(int position) {
Toast.makeText(CamActivity.this, "Changed to page " + position, Toast.LENGTH_SHORT).show();
if(position == 0) {
preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(mPreview);
}
}
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
public void onPageScrollStateChanged(int state) {
}
});
}
}
DDMS 输出：
05-10 09:15:44.696: D/dalvikvm(1135): GC_EXTERNAL_ALLOC freed 55K, 51% free 2682K/5379K, external 1541K/1559K, paused 775ms
05-10 09:15:47.746: D/gralloc_goldfish(1135): Emulator without GPU emulation detected.
05-10 09:19:54.329: D/AndroidRuntime(1135): Shutting down VM
05-10 09:19:54.329: W/dalvikvm(1135): threadid=1: thread exiting with uncaught exception (group=0xb68ad4f0)
05-10 09:19:54.410: E/AndroidRuntime(1135): FATAL EXCEPTION: main
05-10 09:19:54.410: E/AndroidRuntime(1135): java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.view.ViewGroup.addViewInner(ViewGroup.java:1976)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.view.ViewGroup.addView(ViewGroup.java:1871)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.view.ViewGroup.addView(ViewGroup.java:1828)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.view.ViewGroup.addView(ViewGroup.java:1808)
05-10 09:19:54.410: E/AndroidRuntime(1135): at com.app.cam.CamActivity$1.onPageSelected(CamActivity.java:97)
05-10 09:19:54.410: E/AndroidRuntime(1135): at com.viewpagerindicator.TitlePageIndicator.onPageSelected(TitlePageIndicator.java:709)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:438)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.support.v4.view.ViewPager.onTouchEvent(ViewPager.java:1527)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.view.View.dispatchTouchEvent(View.java:3885)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:903)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:942)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:942)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:942)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:942)
05-10 09:19:54.410: E/AndroidRuntime(1135): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1691)
05-10 09:19:54.410: E/AndroidRuntime(1135): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1125)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.app.Activity.dispatchTouchEvent(Activity.java:2096)
05-10 09:19:54.410: E/AndroidRuntime(1135): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1675)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.view.ViewRoot.deliverPointerEvent(ViewRoot.java:2194)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.view.ViewRoot.handleMessage(ViewRoot.java:1878)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.os.Handler.dispatchMessage(Handler.java:99)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.os.Looper.loop(Looper.java:130)
05-10 09:19:54.410: E/AndroidRuntime(1135): at android.app.ActivityThread.main(ActivityThread.java:3683)
05-10 09:19:54.410: E/AndroidRuntime(1135): at java.lang.reflect.Method.invokeNative(Native Method)
05-10 09:19:54.410: E/AndroidRuntime(1135): at java.lang.reflect.Method.invoke(Method.java:507)
05-10 09:19:54.410: E/AndroidRuntime(1135): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
05-10 09:19:54.410: E/AndroidRuntime(1135): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
05-10 09:19:54.410: E/AndroidRuntime(1135): at dalvik.system.NativeStart.main(Native Method)
05-10 09:20:02.030: I/Process(1135): Sending signal. PID: 1135 SIG: 9