我在我的android活动中使用AsyncTask通过内置摄像头捕获图像并在图像视图上显示它。但是发生了错误？我不知道如何解决它。请给出一些解决方案。
这是我的代码：
public class MainActivity extends Activity {
final static int REQUEST_CODE = 1;
Uri imageuri = null;
String ImageID = null;
MainActivity mainActivity = null;
public static ImageView imageview = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ImageButton btn = (ImageButton)findViewById(R.id.imageButton);
imageview = (ImageView)findViewById(R.id.imageView);
btn.setOnClickListener(new View.OnClickListener() {
//Camera Intent
@Override
public void onClick(View v) {
String filename = "awais.jpg";
ContentValues val = new ContentValues();
val.put(MediaStore.Images.Media.TITLE, filename);
imageuri = getContentResolver().insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, val);
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(intent, REQUEST_CODE);
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == REQUEST_CODE && resultCode == RESULT_OK) {
// Toast.makeText(this,"o0k",Toast.LENGTH_SHORT).show();
ImageID = Converturi(imageuri, mainActivity);
new loadphoto().execute("" + ImageID)
;
}
}
public static String Converturi(Uri Imageuri, Activity activity) {
Cursor cursor = null;
int imageid = 0;
try {
String proj[] = {
MediaStore.Images.Media._ID,
MediaStore.Images.Thumbnails._ID
};
cursor = activity.managedQuery(Imageuri, proj, null, null, null);
int index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media._ID);
int thumb = cursor.getColumnIndexOrThrow(MediaStore.Images.Thumbnails._ID);
//int size=cursor.getCount();
int thumbid = 0;
if (cursor.moveToFirst()) {
imageid = cursor.getInt(index);
thumbid = cursor.getInt(thumb);
}
}
finally {
if (cursor != null) {
cursor.close();
}
}
return "" + imageid;
}
public class loadphoto extends AsyncTask<String, Void, Void> {
ProgressDialog dailog = new ProgressDialog(MainActivity.this);
Bitmap mainbitmap;
@Override
protected void onPreExecute() {
dailog.setMessage("Loading");
dailog.show();
}
@Override
protected Void doInBackground(String... urls) {
Bitmap bitmap = null;
Bitmap newbitmap = null;
Uri uri = null;
try {
uri = Uri.withAppendedPath(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, "" + urls[0]);
bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri));
if (bitmap != null) {
newbitmap = Bitmap.createScaledBitmap(bitmap, 170, 170, true);
bitmap.recycle();
if (newbitmap != null) {
mainbitmap = newbitmap;
}
}
}
catch (IOException e) {
cancel(true);
}
return null;
}
@Override
protected void onPostExecute(Void unused) {
dailog.dismiss();
if (mainbitmap != null) {
imageview.setImageBitmap(mainbitmap);
}
}
}
错误：
E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { act=inline-data (has extras) }} to activity {com.example.itinternee.camera/com.example.itinternee.camera.MainActivity}: java.lang.NullPointerException
at android.app.ActivityThread.deliverResults(ActivityThread.java:3367)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:3410)
at android.app.ActivityThread.access$1100(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1304)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5103)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.example.itinternee.camera.MainActivity.Converturi(MainActivity.java:93)
at com.example.itinternee.camera.MainActivity.onActivityResult(MainActivity.java:72)
at android.app.Activity.dispatchActivityResult(Activity.java:5322)
at android.app.ActivityThread.deliverResults(ActivityThread.java:3363)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:3410)
at android.app.ActivityThread.access$1100(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1304)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5103)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：0)
我认为你不需要你的异步函数来加载imageView中的图片.... 首先使用代码启动相机然后进入
btn.setOnClickListener(new View.OnClickListener() {
//Camera Intent
@Override
public void onClick(View v) {
Intent intent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(intent, 0);
}
});
OnActivityResult添加了这个。
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
try {
Bitmap imageCapture = (Bitmap) data.getExtras().get("data");
imageview.setImageBitmap(imageCapture);
} catch (NullPointerException e) {
}
}