src/com/android/launcher3/UninstallDropTarget.java

package com.android.launcher3;

import android.annotation.TargetApi;
import android.content.ComponentName;
import android.content.Context;
import android.os.Build;
import android.os.Bundle;
import android.os.UserManager;
import android.util.AttributeSet;
import android.util.Pair;
import com.android.launcher3.R;
import com.android.launcher3.compat.UserHandleCompat;
import com.android.launcher3.util.Thunk;

public class UninstallDropTarget extends ButtonDropTarget {

    public UninstallDropTarget(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public UninstallDropTarget(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
        // Get the hover color
        mHoverColor = getResources().getColor(R.color.uninstall_target_hover_tint);

        setDrawable(R.drawable.ic_launcher_uninstall_normal);
    }

    @Override
    protected boolean supportsDrop(DragSource source, Object info) {
        return supportsDrop(getContext(), info);
    }

    @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
    public static boolean supportsDrop(Context context, Object info) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {
            UserManager userManager = (UserManager) context.getSystemService(Context.USER_SERVICE);
            Bundle restrictions = userManager.getUserRestrictions();
            if (restrictions.getBoolean(UserManager.DISALLOW_APPS_CONTROL, false)
                    || restrictions.getBoolean(UserManager.DISALLOW_UNINSTALL_APPS, false)) {
                return false;
            }
        }

        Pair<ComponentName, Integer> componentInfo = getAppInfoFlags(info);
        return componentInfo != null && (componentInfo.second & AppInfo.DOWNLOADED_FLAG) != 0;
    }

    /**
     * @return the component name and flags if {@param info} is an AppInfo or an app shortcut.
     */
    private static Pair<ComponentName, Integer> getAppInfoFlags(Object item) {
        if (item instanceof AppInfo) {
            AppInfo info = (AppInfo) item;
            return Pair.create(info.componentName, info.flags);
        } else if (item instanceof ShortcutInfo) {
            ShortcutInfo info = (ShortcutInfo) item;
            ComponentName component = info.getTargetComponent();
            if (info.itemType == LauncherSettings.BaseLauncherColumns.ITEM_TYPE_APPLICATION
                    && component != null) {
                return Pair.create(component, info.flags);
            }
        }
        return null;
    }

    @Override
    public void onDrop(DragObject d) {
        // Differ item deletion
        if (d.dragSource instanceof UninstallSource) {
            ((UninstallSource) d.dragSource).deferCompleteDropAfterUninstallActivity();
        }
        super.onDrop(d);
    }

    @Override
    void completeDrop(final DragObject d) {
        final Pair<ComponentName, Integer> componentInfo = getAppInfoFlags(d.dragInfo);
        final UserHandleCompat user = ((ItemInfo) d.dragInfo).user;
        if (startUninstallActivity(mLauncher, d.dragInfo)) {

            final Runnable checkIfUninstallWasSuccess = new Runnable() {
                @Override
                public void run() {
                    String packageName = componentInfo.first.getPackageName();
                    boolean uninstallSuccessful = !AllAppsList.packageHasActivities(
                            getContext(), packageName, user);
                    sendUninstallResult(d.dragSource, uninstallSuccessful);
                }
            };
            mLauncher.addOnResumeCallback(checkIfUninstallWasSuccess);
        } else {
            sendUninstallResult(d.dragSource, false);
        }
    }

    public static boolean startUninstallActivity(Launcher launcher, Object info) {
        final Pair<ComponentName, Integer> componentInfo = getAppInfoFlags(info);
        final UserHandleCompat user = ((ItemInfo) info).user;
        return launcher.startApplicationUninstallActivity(
                componentInfo.first, componentInfo.second, user);
    }

    @Thunk void sendUninstallResult(DragSource target, boolean result) {
        if (target instanceof UninstallSource) {
            ((UninstallSource) target).onUninstallActivityReturned(result);
        }
    }

    /**
     * Interface defining an object that can provide uninstallable drag objects.
     */
    public static interface UninstallSource {

        /**
         * A pending uninstall operation was complete.
         * @param result true if uninstall was successful, false otherwise.
         */
        void onUninstallActivityReturned(boolean result);

        /**
         * Indicates that an uninstall request are made and the actual result may come
         * after some time.
         */
        void deferCompleteDropAfterUninstallActivity();
    }
}