我想创建一个活动，在该活动中，我可以使用相机或图库上传图像到imageView中。
在我的平板电脑上这个功能正常，但在我的Galaxy S4手机上，在使用相机拍照后无法恢复活动。以下是logcat记录：
在我的平板电脑上这个功能正常，但在我的Galaxy S4手机上，在使用相机拍照后无法恢复活动。以下是logcat记录：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.gianluca.achieveme, PID: 27301
java.lang.RuntimeException: Unable to resume activity {com.example.gianluca.achieveme/com.example.gianluca.achieveme.AchievementCompleted}: java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=null} to activity {com.example.gianluca.achieveme/com.example.gianluca.achieveme.AchievementCompleted}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.net.Uri.getPath()' on a null object reference
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3403)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3434)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2772)
at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:4471)
at android.app.ActivityThread.access$1000(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1455)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5951)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195)
Caused by: java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=null} to activity {com.example.gianluca.achieveme/com.example.gianluca.achieveme.AchievementCompleted}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.net.Uri.getPath()' on a null object reference
at android.app.ActivityThread.deliverResults(ActivityThread.java:4067)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3389)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3434)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2772)
at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:4471)
at android.app.ActivityThread.access$1000(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1455)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5951)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.net.Uri.getPath()' on a null object reference
at com.example.gianluca.achieveme.AchievementCompleted.onActivityResult(AchievementCompleted.java:126)
at android.app.Activity.dispatchActivityResult(Activity.java:6549)
at android.app.ActivityThread.deliverResults(ActivityThread.java:4063)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3389)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3434)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2772)
at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:4471)
at android.app.ActivityThread.access$1000(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1455)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5951)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195)
我看到说使用相机会浪费大量内存，所以我必须使用onSavedInstanceState和onRestoreInstanceState来保存状态，但是我不知道如何操作。你能给我解释一下吗？这里是我的activity的Java代码：
public class AchievementCompleted extends AppCompatActivity implements DatePickerDialog.OnDateSetListener{
public static TextView tvTitle;
public static TextView tvDescription;
public static Button bDate;
public static Button bPosition;
public static Switch switchbutton;
private Uri imageCaptureUri;
private ImageView mImageView;
private static final int PICK_FROM_CAMERA=1;
private static final int PICK_FROM_FILE=2;
private Button bPhoto;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_achievement_completed);
tvTitle = (TextView)findViewById(R.id.titolo);
tvDescription = (TextView)findViewById(R.id.descrizione);
bDate = (Button)findViewById(R.id.data);
switchbutton = (Switch)findViewById(R.id.swtich);
Intent intent = getIntent();
tvTitle.setText(intent.getStringExtra("Titolo"));
tvDescription.setText(intent.getStringExtra("Descrizione"));
switchbutton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
}
});
final String[] items = new String [] {"Scatta foto", "Scegli dalla galleria"};
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.select_dialog_item,items);
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Seleziona l'immagine");
builder.setAdapter(adapter, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
if(which==0){
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
File file = new File(Environment.getExternalStorageDirectory(),"tmp_avatar"+ String.valueOf(System.currentTimeMillis())+".jpg");
imageCaptureUri = Uri.fromFile(file);
try{
intent.putExtra(MediaStore.EXTRA_OUTPUT,imageCaptureUri);
intent.putExtra("return data",true);
startActivityForResult(intent,PICK_FROM_CAMERA);
}catch (Exception ex){
ex.printStackTrace();
}
dialog.cancel();
}else{
Intent intent = new Intent();
intent.setType("image/*");
intent.setAction(Intent.ACTION_GET_CONTENT);
startActivityForResult(Intent.createChooser(intent,"Completa l'azione usando"),PICK_FROM_FILE);
}
}
});
final AlertDialog dialog=builder.create();
mImageView=(ImageView)findViewById(R.id.immagine);
bPhoto = (Button)findViewById(R.id.btnFoto);
bPhoto.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dialog.show();
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if(resultCode!=RESULT_OK)
return;
Bitmap bitmap = null;
String path="";
if(requestCode==PICK_FROM_FILE){
imageCaptureUri=data.getData();
path=getRealPathFromURI(imageCaptureUri);
if(path==null)
path=imageCaptureUri.getPath();
if(path!=null){
BitmapFactory.Options mBitMapOption = new BitmapFactory.Options();
mBitMapOption.inSampleSize=2;
bitmap= BitmapFactory.decodeFile(path,mBitMapOption);
}
}else{
path=imageCaptureUri.getPath();
BitmapFactory.Options mBitMapOption = new BitmapFactory.Options();
mBitMapOption.inSampleSize=2;
bitmap= BitmapFactory.decodeFile(path,mBitMapOption);
}
mImageView.setImageBitmap(bitmap);
}
public String getRealPathFromURI(Uri contentURI){
String[] proj={MediaStore.Images.Media.DATA};
Cursor cursor = managedQuery(contentURI,proj,null,null,null);
if(cursor==null) return null;
int column_index=cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
cursor.moveToFirst();
return cursor.getString(column_index);
}
}
Thank you in advance