Android 開發筆記 - Image Picker 與權限管理

在 Android 6.0 (API:23) 後，就算 AndroidManifest.xml 寫好要權限的部分，但實務上在進行時，依舊要主動要一次，讓用戶感受到真的要權限了：https://developer.android.com/training/permissions/requesting

做 Image Picker 時，若最終要讀取資料，那需要 android.permission.READ_EXTERNAL_STORAGE 權限，以下則是在 MainActivity 運行的範例：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android">

    <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>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
</manifest>

public class MainActivity extends AppCompatActivity {
private static final int REQUEST_SELECT_VIDEO = 1;
private static final int REQUEST_EXTERNAL_STORAGE = 2;
private static String[] PERMISSIONS_STORAGE = {
Manifest.permission.READ_EXTERNAL_STORAGE,
};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

if (ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(this, PERMISSIONS_STORAGE, REQUEST_EXTERNAL_STORAGE);
} else {
request_pick();
}
}

void request_pick() {
final Uri mUri = android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
final Intent mIntent = new Intent(Intent.ACTION_PICK, mUri);
final PackageManager mPackageManager = getPackageManager();
List<ResolveInfo> list = mPackageManager.queryIntentActivities(mIntent, PackageManager.MATCH_DEFAULT_ONLY);
if (list.size() > 1) {
startActivityForResult(
Intent.createChooser(
new Intent(Intent.ACTION_PICK, mUri), "選取圖片"
),
REQUEST_SELECT_VIDEO
);
} else {
startActivityForResult(mIntent, REQUEST_SELECT_VIDEO);
}
}

@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == RESULT_OK) {
if (requestCode == REQUEST_SELECT_VIDEO) {
// ...
// 在處理檔案讀取時，缺少 android.permission.READ_EXTERNAL_STORAGE 會造成 IOException:
// open failed: EACCES (Permission denied)
// ...
}
}
}
}