Full source code to request a READ_EXTERNAL_STORAGE permission at run time, which is necessary since Android 6.0 (Marshmallow), whereas before this permission would be granted at the installation process. For this we will use the checkSelfPermission and requestPermissions methods and show a rationale to the user at the appropriate time with the shouldShowRequestPermissionRationale method
activity_main.xml
?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="tech.codingpoint.permissionrequestexample.MainActivity">
<Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Request Permission"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="tech.codingpoint.permissionrequestexample">
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
MainActivity.java
package tech.codingpoint.permissionrequestexample;
import android.Manifest;
import android.content.DialogInterface;
import android.content.pm.PackageManager;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
private int STORAGE_PERMISSION_CODE = 1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button buttonRequest = findViewById(R.id.button);
buttonRequest.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (ContextCompat.checkSelfPermission(MainActivity.this,
Manifest.permission.READ_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
Toast.makeText(MainActivity.this, "You have already granted this permission!",
Toast.LENGTH_SHORT).show();
} else {
requestStoragePermission();
}
}
});
}
private void requestStoragePermission() {
if (ActivityCompat.shouldShowRequestPermissionRationale(this,
Manifest.permission.READ_EXTERNAL_STORAGE)) {
new AlertDialog.Builder(this)
.setTitle("Permission needed")
.setMessage("This permission is needed because of this and that")
.setPositiveButton("ok", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
ActivityCompat.requestPermissions(MainActivity.this,
new String[] {Manifest.permission.READ_EXTERNAL_STORAGE}, STORAGE_PERMISSION_CODE);
}
})
.setNegativeButton("cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
})
.create().show();
} else {
ActivityCompat.requestPermissions(this,
new String[] {Manifest.permission.READ_EXTERNAL_STORAGE}, STORAGE_PERMISSION_CODE);
}
}
@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();
}
}
}
}