将文件存储到外部存储需要太多时间

Question

>我正在尝试使用本地相机从我的应用程序中拍照。将图像保存在所述文件夹中花费的时间太长。由于这个时间滞后，我使用位图库在我的代码中获得了NullPointerException。

我已经检查了与该问题相关的其他答案，我已经在AndroidManifest.xml中提供了权限，还提供了Easy Permission-implementation'pub.devrel：easypermissions：0.2.1'。我可以在外部存储图像，但图像在 5-10 分钟后显示在文件夹中。然后代码无法读取图像，因为它无法在设备上找到它。它在应用程序崩溃后显示。

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == CAMERA_REQUEST && resultCode == RESULT_OK) {
        Bitmap photo = BitmapFactory.decodeFile(f.getAbsolutePath());
        imageView.setImageBitmap(photo);
        Intent i = new Intent(Intent.ACTION_SEND);
        Uri uri = Uri.fromFile(f);
        i.putExtra(Intent.EXTRA_STREAM, uri);
        try {
            startActivity(Intent.createChooser(i, "Send mail..."));
        } catch (android.content.ActivityNotFoundException ex) {
            Toast.makeText(HomeScreen.this, "There are no email clients installed.", Toast.LENGTH_SHORT).show();
        }
        i.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
        i.setType("message/rfc822");
        i.putExtra(Intent.EXTRA_EMAIL  , new String[]{"[e-mail]"});
        i.putExtra(Intent.EXTRA_SUBJECT, "Subject");
        i.putExtra(Intent.EXTRA_TEXT   , "body of email");

    }
  }

错误显示在此行中 imageView.setImageBitmap(photo);

D/AndroidRuntime: Shutting down VM
 java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1888, result=-1, data=Intent { dat=file:///storage/emulated/0/Pictures/pic/image-9747.jpg flg=0x1 }} to activity {com.example.pic/com.example.pic.HomeScreen}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageBitmap(android.graphics.Bitmap)' on a null object reference
     at android.app.ActivityThread.deliverResults(ActivityThread.java:3779)
     at android.app.ActivityThread.handleSendResult(ActivityThread.java:3822)
     at android.app.ActivityThread.access$1400(ActivityThread.java:155)
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1429)
     at android.os.Handler.dispatchMessage(Handler.java:102)
     at android.os.Looper.loop(Looper.java:152)
     at android.app.ActivityThread.main(ActivityThread.java:5497)
     at java.lang.reflect.Method.invoke(Native Method)
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
  Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageBitmap(android.graphics.Bitmap)' on a null object reference```

Answer 1

你有没有在你的onCreate()上添加这个

imageView = (ImageView)findViewById(R.id.imageView2);

Manifest.xml上的ImageView声明样本

 <ImageView
  android:id="@+id/uncheck_disp_act"
  android:layout_width="25dp"
  android:layout_height="25dp"
  app:srcCompat="@drawable/uncheck" />