java - 无法在 Android 中显示画廊中选定的图像

Question

我想从图库中选择图像并加载或在 Activity 中显示它。但代码无法正常工作。它只能从手机图库中选择图像，但不显示所选图像。检查 logcat 发现这些错误。我在下面提供了 java 文件、xml 文件和 list 。

11-15 16:31:23.795 18921-18921/com.example.emma.gallaryview E/MultiWindowProxy: getServiceInstance failed!
11-15 16:31:34.970 18921-18921/com.example.emma.gallaryview E/BitmapFactory: Unable to decode stream: java.io.FileNotFoundException: /storage/emulated/0/DCIM/Camera/IMG_20171114_202150.jpg: open failed: EACCES (Permission denied)

java文件

    public class MainActivity extends AppCompatActivity {
    private static int RESULT_LOAD_IMG = 1;
    String imgDecodableString;

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

    public void loadImagefromGallery(View view) {
        // Create intent to Open Image applications like Gallery, Google Photos
        Intent galleryIntent = new Intent(Intent.ACTION_PICK,
                android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
        // Start the Intent
        startActivityForResult(galleryIntent, RESULT_LOAD_IMG);
    }


    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        try {
            // When an Image is picked
            if (requestCode == RESULT_LOAD_IMG && resultCode == RESULT_OK
                    && null != data) {
                // Get the Image from data

                Uri selectedImage = data.getData();
                String[] filePathColumn = {MediaStore.Images.Media.DATA};

                // Get the cursor
                Cursor cursor = getContentResolver().query(selectedImage,
                        filePathColumn, null, null, null);
                // Move to first row
                cursor.moveToFirst();

                int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
                imgDecodableString = cursor.getString(columnIndex);
                cursor.close();
                ImageView imgView = (ImageView) findViewById(R.id.imgView);
                // Set the Image in ImageView after decoding the String
                imgView.setImageBitmap(BitmapFactory
                        .decodeFile(imgDecodableString));

            } else {
                Toast.makeText(this, "You haven't picked Image",
                        Toast.LENGTH_LONG).show();
            }
        } catch (Exception e) {
            Toast.makeText(this, "Something went wrong", Toast.LENGTH_LONG)
                    .show();
        }

    }

}

xml文件

 <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <ImageView
        android:id="@+id/imgView"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1" >
    </ImageView>

    <Button
        android:id="@+id/buttonLoadPicture"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_weight="0"
        android:onClick="loadImagefromGallery"
        android:text="Load Picture" >
    </Button>

</LinearLayout>

和 list

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.emma.gallaryview">
    <uses-permission android:name="android.permission.CAMERA"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-feature android:name="android.hardware.camera"/>
    <uses-feature android:name="android.hardware.camera.autofocus"/>
    <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>

Answer 1

在 Android 6+ 上，您必须添加代码来要求应用的用户确认您在 list 中请求的权限。

Google 获取运行时权限。

此外，您的代码过于复杂。您应该只为获得的 uri 打开一个输入流，然后让位图工厂从 steam 中解码。

InputStream is = getContentResolver().openInputStream(data.getData());

然后使用

BitmapFactory.decodeStream(is).

最后:如果decodeStream 在很多设备上返回null，请不要感到惊讶。就像decodeFile 一样。