在多視窗模式下拖曳

搭載 Android 7.0 (API 級別 24) 以上版本的裝置支援多視窗模式，可讓使用者透過拖曳的方式，在不同應用程式間移動資料。

作業開始所在的來源應用程式會提供資料。作業結束的目標應用程式會接收資料。

使用者開始拖曳內容時，來源應用程式應設定 DRAG_FLAG_GLOBAL 旗標，以表示使用者可將資料拖曳到其他應用程式。

由於資料會跨應用程式邊界移動，因此應用程式會使用內容 URI 共用資料的存取權。這項功能需要下列項目：

• 視來源應用程式要授予目標應用程式的資料讀取或寫入權限而定，來源應用程式必須設定 DRAG_FLAG_GLOBAL_URI_READ 或 DRAG_FLAG_GLOBAL_URI_WRITE，或兩者皆設定。
• 如果目標應用程式不再需要存取拖曳的資料，目標應用程式就必須立即呼叫 requestDragAndDropPermissions()。如果目標應用程式不再需要存取拖曳的資料，應用程式就可以在 requestDragAndDropPermissions() 傳回的物件上呼叫 release()。否則，當所屬活動遭到刪除時，權限就會撤銷。如果實作需要啟動新的 Activity 來處理已捨棄的 URI，您必須為新的 Activity 授予相同的權限。您必須設定剪輯片段資料和標記：

  Kotlin

  intent.setClipData(clipData)
  intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
  

  Java

  intent.setClipData(clipData);
  intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
  

下列程式碼片段說明如何在使用者推送作業發生後，立即撤銷拖曳資料的唯讀存取權。如需更完整的範例，請參閱 GitHub 上的 Drag-And-Drop 範例。

來源活動

Kotlin

// Drag a file stored in an images/ directory in internal storage.
val internalImagesDir = File(context.filesDir, "images")
val imageFile = File(internalImagesDir, imageFilename)
val uri = FileProvider.getUriForFile(context, contentAuthority, imageFile)

val listener = OnDragStartListener@{ view: View, _: DragStartHelper ->
    val clipData = ClipData(ClipDescription("Image Description",
                                            arrayOf("image/*")),
                            ClipData.Item(uri))
    // Must include DRAG_FLAG_GLOBAL to permit dragging data between apps.
    // This example provides read-only access to the data.
    val flags = View.DRAG_FLAG_GLOBAL or View.DRAG_FLAG_GLOBAL_URI_READ
    return@OnDragStartListener view.startDragAndDrop(clipData,
                                                     View.DragShadowBuilder(view),
                                                     null,
                                                     flags)
}

// Container where the image originally appears in the source app.
val srcImageView = findViewById<ImageView>(R.id.imageView)

// Detect and start the drag event.
DragStartHelper(srcImageView, listener).apply {
    attach()
}

Java

// Drag a file stored in an images/ directory in internal storage.
File internalImagesDir = new File(context.getFilesDir(), "images");
File imageFile = new File(internalImagesDir, imageFilename);
final Uri uri = FileProvider.getUriForFile(context, contentAuthority, imageFile);

// Container where the image originally appears in the source app.
ImageView srcImageView = findViewById(R.id.imageView);

// Enable the view to detect and start the drag event.
new DragStartHelper(srcImageView, (view, helper) -> {
    ClipData clipData = new ClipData(new ClipDescription("Image Description",
                                                          new String[] {"image/*"}),
                                     new ClipData.Item(uri));
    // Must include DRAG_FLAG_GLOBAL to permit dragging data between apps.
    // This example provides read-only access to the data.
    int flags = View.DRAG_FLAG_GLOBAL | View.DRAG_FLAG_GLOBAL_URI_READ;
    return view.startDragAndDrop(clipData,
                                 new View.DragShadowBuilder(view),
                                 null,
                                 flags);
}).attach();

目標活動

Kotlin

// Container where the image is to be dropped in the target app.
val targetImageView = findViewById<ImageView>(R.id.imageView)

targetImageView.setOnDragListener { view, event ->

    when (event.action) {

        ACTION_DROP -> {
            val imageItem: ClipData.Item = event.clipData.getItemAt(0)
            val uri = imageItem.uri

            // Request permission to access the image data being dragged into
            // the target activity's ImageView element.
            val dropPermissions = requestDragAndDropPermissions(event)
            (view as ImageView).setImageURI(uri)

            // Release the permission immediately afterward because it's no
            // longer needed.
            dropPermissions.release()
            return@setOnDragListener true
        }

        // Implement logic for other DragEvent cases here.

        // An unknown action type is received.
        else -> {
            Log.e("DragDrop Example", "Unknown action type received by View.OnDragListener.")
            return@setOnDragListener false
        }

    }
}

Java

// Container where the image is to be dropped in the target app.
ImageView targetImageView = findViewById(R.id.imageView);

targetImageView.setOnDragListener( (view, event) -> {

    switch (event.getAction()) {

        case ACTION_DROP:
            ClipData.Item imageItem = event.getClipData().getItemAt(0);
            Uri uri = imageItem.getUri();

            // Request permission to access the image data being dragged into
            // the target activity's ImageView element.
            DragAndDropPermissions dropPermissions =
                requestDragAndDropPermissions(event);

            ((ImageView)view).setImageURI(uri);

            // Release the permission immediately afterward because it's no
            // longer needed.
            dropPermissions.release();

            return true;

        // Implement logic for other DragEvent cases here.

        // An unknown action type was received.
        default:
            Log.e("DragDrop Example","Unknown action type received by View.OnDragListener.");
            break;
    }

    return false;
});