我正在制作一个录像机，并且logcat上的下一个异常引起了我的注意，我怀疑错误是在onClick函数中，因为代码在添加此函数之前正常工作。
示例代码在此处：
package com.example.video;
import java.io.IOException;
import android.media.CamcorderProfile;
import android.media.MediaRecorder;
import android.os.Build;
import android.os.Bundle;
import android.annotation.SuppressLint;
import android.annotation.TargetApi;
import android.app.Activity;
import android.hardware.Camera;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.FrameLayout;
public class MainActivity extends Activity
{
private Camera mCamera;
private CameraPreview mPreview;
MediaRecorder mMediaRecorder;
private boolean isRecording = false;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Create an instance of Camera
mCamera = getCameraInstance();
mPreview = new CameraPreview(this, mCamera);
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(mPreview);
}
@TargetApi(Build.VERSION_CODES.GINGERBREAD)
public static Camera getCameraInstance(){
int cameraCount = 0;
Camera cam = null;
Camera.CameraInfo cameraInfo = new Camera.CameraInfo();
cameraCount = Camera.getNumberOfCameras();
for ( int camIdx = 0; camIdx < cameraCount; camIdx++ ) {
Camera.getCameraInfo( camIdx, cameraInfo );
if ( cameraInfo.facing == Camera.CameraInfo.CAMERA_FACING_FRONT ) {
try {
cam = Camera.open( camIdx );
} catch (RuntimeException e) {
Log.e("error", "Camera failed to open: " + e.getLocalizedMessage());
}
}
}
return cam;
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
public void onClick(View v)
{
if (isRecording) {
// stop recording and release camera
mMediaRecorder.stop(); // stop the recording
releaseMediaRecorder(); // release the MediaRecorder object
mCamera.lock(); // take camera access back from MediaRecorder
// inform the user that recording has stopped
isRecording = false;
} else {
// initialize video camera
if (prepareVideoRecorder()) {
// Camera is available and unlocked, MediaRecorder is prepared,
// now you can start recording
mMediaRecorder.start();
// inform the user that recording has started
isRecording = true;
} else {
// prepare didn't work, release the camera
releaseMediaRecorder();
// inform user
}
}
}
@SuppressLint("InlinedApi")
private boolean prepareVideoRecorder(){
mCamera = getCameraInstance();
mMediaRecorder = new MediaRecorder();
// Step 1: Unlock and set camera to MediaRecorder
mCamera.unlock();
mMediaRecorder.setCamera(mCamera);
// Step 2: Set sources
mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.CAMCORDER);
mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);
// Step 3: Set a CamcorderProfile (requires API Level 8 or higher)
mMediaRecorder.setProfile(CamcorderProfile.get(CamcorderProfile.QUALITY_HIGH));
// Step 4: Set output file
mMediaRecorder.setOutputFile("D://");
// Step 5: Set the preview output
mMediaRecorder.setPreviewDisplay(mPreview.getHolder().getSurface());
// Step 6: Prepare configured MediaRecorder
try {
mMediaRecorder.prepare();
} catch (IllegalStateException e) {
Log.d("error", "IllegalStateException preparing MediaRecorder: " + e.getMessage());
releaseMediaRecorder();
return false;
} catch (IOException e) {
Log.d("error", "IOException preparing MediaRecorder: " + e.getMessage());
releaseMediaRecorder();
return false;
}
mMediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
mMediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.DEFAULT);
mMediaRecorder.setVideoEncoder(MediaRecorder.VideoEncoder.DEFAULT);
return true;
}
private void releaseMediaRecorder(){
if (mMediaRecorder != null) {
mMediaRecorder.reset(); // clear recorder configuration
mMediaRecorder.release(); // release the recorder object
mMediaRecorder = null;
mCamera.lock(); // lock camera for later use
}
}
@Override
protected void onPause() {
super.onPause();
releaseMediaRecorder(); // if you are using MediaRecorder, release it first
releaseCamera(); // release the camera immediately on pause event
}
private void releaseCamera(){
if (mCamera != null){
mCamera.release(); // release the camera for other applications
mCamera = null;
}
}
}
这是logcat窗口：
07-22 10:56:08.243:
D/libEGL(31644): loaded /system/lib/egl/libEGL_VIVANTE.so
07-22 10:56:08.250: D/libEGL(31644): loaded /system/lib/egl/libGLESv1_CM_VIVANTE.so
07-22 10:56:08.260: D/libEGL(31644): loaded /system/lib/egl/libGLESv2_VIVANTE.so
07-22 10:56:08.350: D/OpenGLRenderer(31644): Enabling debug mode 0
07-22 10:56:13.083: E/error(31644): Camera failed to open: Fail to connect to camera service
07-22 10:56:13.093: D/AndroidRuntime(31644): Shutting down VM
07-22 10:56:13.093: W/dalvikvm(31644): threadid=1: thread exiting with uncaught exception (group=0x40aa61f8)
07-22 10:56:13.117: E/AndroidRuntime(31644): FATAL EXCEPTION: main
07-22 10:56:13.117: E/AndroidRuntime(31644): java.lang.IllegalStateException: Could not execute method of the activity
07-22 10:56:13.117: E/AndroidRuntime(31644): at android.view.View$1.onClick(View.java:3052)
07-22 10:56:13.117: E/AndroidRuntime(31644):at android.view.View.performClick(View.java:3519)
07-22 10:56:13.117: E/AndroidRuntime(31644): at android.view.View$PerformClick.run(View.java:14143)
07-22 10:56:13.117: E/AndroidRuntime(31644): at android.os.Handler.handleCallback(Handler.java:605)
07-22 10:56:13.117: E/AndroidRuntime(31644): at android.os.Handler.dispatchMessage(Handler.java:92)
07-22 10:56:13.117: E/AndroidRuntime(31644): at android.os.Looper.loop(Looper.java:137)
07-22 10:56:13.117: E/AndroidRuntime(31644): at android.app.ActivityThread.main(ActivityThread.java:4521)
07-22 10:56:13.117: E/AndroidRuntime(31644): at java.lang.reflect.Method.invokeNative(Native Method)
07-22 10:56:13.117: E/AndroidRuntime(31644): at java.lang.reflect.Method.invoke(Method.java:511)
07-22 10:56:13.117: E/AndroidRuntime(31644): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:762)
07-22 10:56:13.117: E/AndroidRuntime(31644): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:529)
07-22 10:56:13.117: E/AndroidRuntime(31644): at dalvik.system.NativeStart.main(Native Method)
07-22 10:56:13.117: E/AndroidRuntime(31644): Caused by: java.lang.reflect.InvocationTargetException
07-22 10:56:13.117: E/AndroidRuntime(31644): at java.lang.reflect.Method.invokeNative(Native Method)
07-22 10:56:13.117: E/AndroidRuntime(31644): at java.lang.reflect.Method.invoke(Method.java:511)
07-22 10:56:13.117: E/AndroidRuntime(31644): at android.view.View$1.onClick(View.java:3047)
07-22 10:56:13.117: E/AndroidRuntime(31644): ... 11 more
07-22 10:56:13.117: E/AndroidRuntime(31644): Caused by: java.lang.NullPointerException
07-22 10:56:13.117: E/AndroidRuntime(31644): at com.example.video.MainActivity.prepareVideoRecorder(MainActivity.java:109)
07-22 10:56:13.117: E/AndroidRuntime(31644): at com.example.video.MainActivity.onClick(MainActivity.java:81)
07-22 10:56:13.117: E/AndroidRuntime(31644): ... 14 more