I started a new project in Android Studio with: empty activity, Java, API 29, Android 10.0 (Q)
I added permissions to AndroidManifest.xml
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
I added ImageView and a Button to activity_main.xml
<Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="80dp"
android:text="button"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<ImageView
android:id="@+id/my_image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/button"
/>
I loaded an image in MainActivity.java - Permissions are checked at run time, after a button click. Then after another button click the image should be viewed. The code also contains a few checks for correct activity.
package mrppanther.com.example.read_image;
import android.Manifest;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import java.io.File;
public class MainActivity extends AppCompatActivity {
private int STORAGE_PERMISSION_CODE = 1;
private int new_state = 1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// NOTE: use a button to request activity
Button buttonRequest = findViewById(R.id.button);
buttonRequest.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// NOTE: declare "myfile", this is want I want to view
File myfile = new File("/storage/emulated/0/Pictures/henry1.jpg");
// NOTE: on the 1st click, check permissions
if (new_state == 1) {
requestStoragePermission();
new_state = 2; // NOTE: move to the next state, on the next click
// NOTE: on the 2nd click, view image
} else {
// NOTE: check that the "myfile"" exists
if (myfile.exists()) {
Log.i("myfile", "FILE EXISTS PASS! " + myfile);
} else {
Log.i("myfile", "FILE ABSENT FAIL! " + myfile);
}
// NOTE: declare "myimage"
ImageView myimage = (ImageView) findViewById(R.id.my_image);
// NOTE: experimenting with options did not help
BitmapFactory.Options options=new BitmapFactory.Options();
//options.inJustDecodeBounds=true;
options.inSampleSize=1;
// ERROR: E/BitmapFactory: Unable to decode stream: java.io.FileNotFoundException:
// ERROR: /storage/emulated/0/Pictures/henry1.jpg: open failed: EACCES (Permission denied)
Bitmap bitmap = BitmapFactory.decodeFile(String.valueOf(myfile), options);
myimage.setImageBitmap(bitmap);
// NOTE: here is a test to check "myimage" is correct
// NOTE: this works OK, and image from drawable resource is displayed
// myimage.setImageResource(R.drawable.henry1);
new_state = 1; // NOTE: go back to the 1st state, on the next click
}
}
}); // NOTE: this is the end of button activity
}
// NOTE: request permission to read storage, at run time
private void requestStoragePermission() {
ActivityCompat.requestPermissions(this,
new String[]{Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE}, STORAGE_PERMISSION_CODE);
// NOTE: here is a test which sets the wrong permission
// new String[]{Manifest.permission.READ_PHONE_NUMBERS,Manifest.permission.READ_PHONE_STATE}, STORAGE_PERMISSION_CODE);
}
// NOTE: check read permission is granted, at run time
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
if (requestCode == STORAGE_PERMISSION_CODE) {
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
Toast.makeText(this, "Permission GRANTED", Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(this, "Permission DENIED", Toast.LENGTH_SHORT).show();
}
}
}
}
Results: I saw the error message below, and the image was not displayed. However, the run time permission check indicated "Permission GRANTED". Finally I rebooted my Tablet. I checked the app is allowed access to storage (in settings, app, storage permission). I reran the app with USB disconnected, but the image was not displayed.
I/myfile: FILE EXISTS PASS! /storage/emulated/0/Pictures/henry1.jpg
E/BitmapFactory: Unable to decode stream: java.io.FileNotFoundException: /storage/emulated/0/Pictures/henry1.jpg: open failed: EACCES (Permission denied)
