OnClick 的另一种书写

public class ItemClickHandler {

    public static final View.OnClickListener INSTANCE = ItemClickHandler::onItemClick;

    private static void onItemClick(View v) {

        switch (v.getId()) {
            case R.id.btn_1:
                Toast.makeText(v.getContext().getApplicationContext(), "button1", Toast.LENGTH_SHORT).show();
                break;
            case R.id.btn_2:
                Toast.makeText(v.getContext().getApplicationContext(), "button2", Toast.LENGTH_SHORT).show();
                break;
            case R.id.btn_3:
                Toast.makeText(v.getContext().getApplicationContext(), "button2", Toast.LENGTH_SHORT).show();
                break;
            default:
                break;
        }
    }

}

public class TestActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        findViewById(R.id.btn_1).setOnClickListener(ItemClickHandler.INSTANCE);

    }
}

public class NavigationView extends RelativeLayout {

    protected void bindClick() {
        findViewById(R.id.btn_2).setOnClickListener(ItemClickHandler.INSTANCE);
    }
}


public class BottomView extends RelativeLayout {

    protected void bindClick() {
        findViewById(R.id.btn_3).setOnClickListener(ItemClickHandler.INSTANCE);
    }
}

/**
 * Class for handling clicks on workspace and all-apps items
 */
public class ItemClickHandler {

    /**
     * Instance used for click handling on items
     */
    public static final OnClickListener INSTANCE = ItemClickHandler::onClick;

    //点击事件
    private static void onClick(View v) {
        // Make sure that rogue clicks don't get through while allapps is launching, or after the
        // view has detached (it's possible for this to happen if the view is removed mid touch).
        if (v.getWindowToken() == null) {
            return;
        }

        Launcher launcher = Launcher.getLauncher(v.getContext());
        if (!launcher.getWorkspace().isFinishedSwitchingState()) {
            return;
        }

        Object tag = v.getTag();
        if (tag instanceof ShortcutInfo) {
            onClickAppShortcut(v, (ShortcutInfo) tag, launcher);
        } else if (tag instanceof FolderInfo) {
            if (v instanceof FolderIcon) {
                onClickFolderIcon(v);
            }
        } else if (tag instanceof AppInfo) {
            //点击 icon 启动应用
            startAppShortcutOrInfoActivity(v, (AppInfo) tag, launcher);
        } else if (tag instanceof LauncherAppWidgetInfo) {
            if (v instanceof PendingAppWidgetHostView) {
                onClickPendingWidget((PendingAppWidgetHostView) v, launcher);
            }
        }
    }
  //...
}