在我使用单个按钮的主要活动中，单击以下活动启动以使用 android 中的默认相机应用程序拍摄图像，然后录制声音。
但是，每当我单击主要活动中的按钮时，我都会收到此错误：
java.lang.RuntimeException: Unable to start activity
ComponentInfo{com.naviiid.soundshot/com.naviiid.soundshot.MicroFilm}:
java.lang.NullPointerException
相机应用程序启动有一点，但在此之前我的应用程序已经停止！这是代码（对不起，代码有点长）：
package com.naviiid.soundshot;
import java.io.File
import java.util.Calendar;
import android.R.drawable;
import android.app.Activity;
import android.content.Intent;
import android.graphics.drawable.Drawable;
import android.media.MediaRecorder;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ImageView;
import android.widget.Toast;
public class MicroFilm extends Activity {
private static final int CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE = 100;
private Uri imageUri;
public static final int MEDIA_TYPE_IMAGE = 1;
public static final int MEDIA_TYPE_VIDEO = 2;
private static File mediaStorageDir;
private ImageView image;
private ImageView record;
private ImageView save;
private ImageView capture;
private boolean visibleButtons = true;
private MediaRecorder soundRecorder;
private String mediaFilePath;
private static Calendar cal;
boolean recording = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_micro_film);
String mediaState = Environment.getExternalStorageState();
if (!mediaState.equals(Environment.MEDIA_MOUNTED)){
Toast.makeText(MicroFilm.this, "Media unmounted! \n Mount media firts..", Toast.LENGTH_LONG).show();
Log.d("StorageState", "Media Unmounted");
finish();
}
mediaStorageDir = new File(Environment
.getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM)
.getAbsolutePath()
+ "/MicroFilm");
takePicture(); // this method will capture image from camera intent and
// returns to main activity if user cancels
// View things
image = (ImageView) findViewById(R.id.imageViewPicture);
record = (ImageView) findViewById(R.id.imageViewMic);
save = (ImageView) findViewById(R.id.imageViewSave);
capture = (ImageView) findViewById(R.id.imageViewCapture);
setBackgroundImage(); // shows taken picture
captureSound(); // prepares for recording, recording starts with imageButton click
}
private void captureSound() {
// prepare things to record
soundRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
soundRecorder.setOutputFormat(MediaRecorder.OutputFormat.AMR_NB);
soundRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
File soundFile = getNewSoundFile();
soundRecorder.setOutputFile(soundFile.getAbsolutePath());
try{
soundRecorder.prepare();
}catch (Exception e) {
Log.d("SoundRecorder", "unable to prepare");
Toast.makeText(MicroFilm.this, "Mic in use", Toast.LENGTH_SHORT).show();
return;
}
//listeners
soundRecorderListeners();
}
private void soundRecorderListeners() {
record.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
if (recording){
soundRecorder.stop();
soundRecorder.release();
recording = false;
record.setBackgroundResource(drawable.ic_btn_speak_now);
}else{
soundRecorder.start();
recording = true;
record.setBackgroundResource(drawable.presence_audio_busy);
}
}
});
}
private File getNewSoundFile() {
// Create a media file name
String timeStamp;
cal = Calendar.getInstance();
timeStamp = "" + cal.get(Calendar.YEAR) + cal.get(Calendar.MONTH) + 1
+ cal.get(Calendar.DAY_OF_MONTH) + "_"
+ cal.get(Calendar.HOUR_OF_DAY) + cal.get(Calendar.MINUTE)
+ cal.get(Calendar.SECOND);
mediaFilePath = mediaStorageDir.getAbsolutePath() + "/AUD_" + timeStamp
+ ".amr";
return new File(mediaFilePath);
}
private void setBackgroundImage() {
// shows taken picture in background
image.setImageDrawable(Drawable.createFromPath(imageUri.getPath()));
image.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
if (visibleButtons) {
record.setVisibility(View.INVISIBLE);
save.setVisibility(View.INVISIBLE);
capture.setVisibility(View.INVISIBLE);
visibleButtons = false;
} else {
record.setVisibility(View.VISIBLE);
save.setVisibility(View.VISIBLE);
capture.setVisibility(View.VISIBLE);
visibleButtons = true;
}
}
});
}
private void takePicture() {
Intent camera = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
imageUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE); // create a file to
// save the image
camera.putExtra(MediaStore.EXTRA_OUTPUT, imageUri); // set the image file
// name
// start the image captugetOutputMediaFileUrire Intent
startActivityForResult(camera, CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE);
}
/** Create a file Uri for saving an image or video */
private static Uri getOutputMediaFileUri(int type) {
return Uri.fromFile(getOutputMediaFile(type));
}
/** Create a File for saving an image or video */
private static File getOutputMediaFile(int type) {
// To be safe, you should check that the SDCard is mounted
// using Environment.getExternalStorageState() before doing this.
// Environment
// .getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
// "MyCameraApp");
// This location works best if you want the created images to be shared
// between applications and persist after your app has been uninstalled.
// Create the storage directory if it does not exist
if (!mediaStorageDir.exists()) {
if (!mediaStorageDir.mkdirs()) {
Log.d("MicroFilm", "failed to create directory");
return null;
}
}
// Create a media file name
String timeStamp;
cal = Calendar.getInstance();
timeStamp = "" + cal.get(Calendar.YEAR) + cal.get(Calendar.MONTH) + 1
+ cal.get(Calendar.DAY_OF_MONTH) + "_"
+ cal.get(Calendar.HOUR_OF_DAY) + cal.get(Calendar.MINUTE)
+ cal.get(Calendar.SECOND);
File mediaFile;
if (type == MEDIA_TYPE_IMAGE) {
mediaFile = new File(mediaStorageDir.getPath() + File.separator
+ "IMG_" + timeStamp + ".jpg");
} else if (type == MEDIA_TYPE_VIDEO) {
mediaFile = new File(mediaStorageDir.getPath() + File.separator
+ "VID_" + timeStamp + ".mp4");
} else {
return null;
}
return mediaFile;
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE) {
if (resultCode == RESULT_OK) {
// Image captured and saved to fileUri specified in the Intent
Toast.makeText(MicroFilm.this, "Image saved", Toast.LENGTH_LONG).show();
} else if (resultCode == RESULT_CANCELED) {
finish();
} else {
// Image capture failed, advise user
}
}
}
}
感谢您的帮助 ：）