android - Draggable drawer with a handle (instead of action bar) on top of other apps

Question

Background

We all know we can use a navigation drawer as a new way to navigate in an app (even with a library, like this one) .

We also know that some apps can float above others (as shown on AirCalc, and done like so) ,using a SYSTEM_ALERT_WINDOW permission.

I've noticed that some apps combine expanding & collapsing of views that are on top , like the next ones:

• callerid
• Sidebar Lite
• Easy Controller-Control Center

and many more...

The problem

We need to merge the 2 concepts of being on top of other apps and allow dragging a handle to show the content on its left side (like a navigation drawer)

Maybe this could show what I mean:

As far as I know, putting anything on top using a system-alert permission requires knowing the size of the view.

However, this is different, since i can't set it to be the entire screen because i don't want to block the rest of the screen in case the user sees only the handle of the navigation drawer.

The question

Is it possible to merge the 2 concepts ?

How would I allow all states to behave nicely while being on top?

for avoiding blocking of touches , I would also like to allow the user to drag the handle up and down, or maybe customize its position in some way.

Answer 1

Based on a few ideas from https://github.com/NikolaDespotoski/DrawerLayoutEdgeToggle I have implemented a much simpler version of a handle for the NavigationDrawer.

Use like this:

View drawer = findViewById(R.id.drawer);
float verticalOffset = 0.2f;
DrawerHandle.attach(drawer, R.layout.handle, verticalOffset);

DrawerHandle:

import android.content.Context;
import android.graphics.Point;
import android.os.Build;
import android.support.v4.view.GravityCompat;
import android.support.v4.view.ViewCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v4.widget.ViewDragHelper;
import android.view.Display;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.FrameLayout;

public class DrawerHandle implements DrawerLayout.DrawerListener {
    public static final String TAG = "DrawerHandle";

    private ViewGroup mRootView;
    private DrawerLayout mDrawerLayout;
    private View mHandle;
    private View mDrawer;

    private float mVerticalOffset;
    private int mGravity;
    private WindowManager mWM;
    private Display mDisplay;
    private Point mScreenDimensions = new Point();

    private OnClickListener mHandleClickListener = new OnClickListener(){

        @Override
        public void onClick(View v) {
            if(!mDrawerLayout.isDrawerOpen(mGravity)) mDrawerLayout.openDrawer(mGravity);
            else mDrawerLayout.closeDrawer(mGravity);
        }

    };

    private OnTouchListener mHandleTouchListener = new OnTouchListener() {
        private static final int MAX_CLICK_DURATION = 200;
        private long startClickTime;
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            switch (event.getAction()) {
                case MotionEvent.ACTION_DOWN: {
                    startClickTime = System.currentTimeMillis();
                    break;
                }
                case MotionEvent.ACTION_UP: {
                    if(System.currentTimeMillis() - startClickTime < MAX_CLICK_DURATION) {
                        v.performClick();
                        return true;
                    }
                }
            }
            MotionEvent copy = MotionEvent.obtain(event);
            copy.setEdgeFlags(ViewDragHelper.EDGE_ALL);
            copy.setLocation(event.getRawX() + (mGravity == Gravity.LEFT || mGravity == GravityCompat.START ? -mHandle.getWidth()/2 : mHandle.getWidth() / 2), event.getRawY());
            mDrawerLayout.onTouchEvent(copy);
            copy.recycle();
            return true;
        }
    };

    private int getDrawerViewGravity(View drawerView) {
        final int gravity = ((DrawerLayout.LayoutParams) drawerView.getLayoutParams()).gravity;
        return GravityCompat.getAbsoluteGravity(gravity, ViewCompat.getLayoutDirection(drawerView));
    }

    private float getTranslation(float slideOffset){
        return (mGravity == GravityCompat.START || mGravity == Gravity.LEFT) ? slideOffset*mDrawer.getWidth() : -slideOffset*mDrawer.getWidth();
    }

    private void updateScreenDimensions() {

        if (Build.VERSION.SDK_INT >= 13) {
            mDisplay.getSize(mScreenDimensions);
        } else {
            mScreenDimensions.x = mDisplay.getWidth();
            mScreenDimensions.y = mDisplay.getHeight();
        }
    }

    private DrawerHandle(DrawerLayout drawerLayout, View drawer, int handleLayout, float handleVerticalOffset) {
        mDrawer = drawer;
        mGravity = getDrawerViewGravity(mDrawer);
        mDrawerLayout = drawerLayout;
        mRootView = (ViewGroup)mDrawerLayout.getRootView();
        LayoutInflater inflater = (LayoutInflater) mDrawerLayout.getContext().getSystemService( Context.LAYOUT_INFLATER_SERVICE );
        mHandle = inflater.inflate(handleLayout, mRootView, false);
        mWM = (WindowManager) mDrawerLayout.getContext().getSystemService(Context.WINDOW_SERVICE);
        mDisplay = mWM.getDefaultDisplay();

        mHandle.setOnClickListener(mHandleClickListener);   
        mHandle.setOnTouchListener(mHandleTouchListener);
        mRootView.addView(mHandle, new FrameLayout.LayoutParams(mHandle.getLayoutParams().width, mHandle.getLayoutParams().height, mGravity));
        setVerticalOffset(handleVerticalOffset);
        mDrawerLayout.setDrawerListener(this);
    }

    public static DrawerHandle attach(View drawer, int handleLayout, float verticalOffset) {
        if (!(drawer.getParent() instanceof DrawerLayout)) throw new IllegalArgumentException("Argument drawer must be direct child of a DrawerLayout");
        return new DrawerHandle((DrawerLayout)drawer.getParent(), drawer, handleLayout, verticalOffset);
    }

    public static DrawerHandle attach(View drawer, int handleLayout) {
        return attach(drawer, handleLayout, 0);
    }

    @Override
    public void onDrawerClosed(View arg0) {
    }

    @Override
    public void onDrawerOpened(View arg0) {

    }

    @Override
    public void onDrawerSlide(View arg0, float slideOffset) {
        float translationX = getTranslation(slideOffset);
        mHandle.setTranslationX(translationX);
    }

    @Override
    public void onDrawerStateChanged(int arg0) {

    }

    public View getView(){
        return mHandle;
    }

    public View getDrawer() {
        return mDrawer;
    }

    public void setVerticalOffset(float offset) {
        updateScreenDimensions();
        mVerticalOffset = offset;
        mHandle.setY(mVerticalOffset*mScreenDimensions.y);
    }
}

Layout:

<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >        

        <RelativeLayout 
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            >

            <com.fscz.views.BounceViewPager
                android:id="@+id/content_pager"
                android:layout_width="match_parent"
                android:layout_height="match_parent" 
                android:layout_centerInParent="true"
                />

            <com.fscz.views.CirclePageIndicator
                android:id="@+id/content_indicator"
                android:layout_height="wrap_content"
                android:layout_width="wrap_content" 
                android:padding="10dp"
                android:layout_centerHorizontal="true"
                android:layout_alignParentBottom="true"
                android:layout_marginTop="100dp"
                style="@style/link"
                />

        </RelativeLayout>

    <LinearLayout
            android:id="@+id/drawer"
            android:layout_width="240dp"
            android:layout_height="match_parent"
            android:layout_gravity="right"
            android:orientation="vertical"
            android:padding="20dp"
            android:background="@color/black_transparent"
            >
            <TextView
                android:layout_width="240dp"
                android:layout_height="wrap_content"
                style="@style/text"
                android:text="@string/collections"
                android:paddingBottom="20dp"
                />
            <ListView 
                android:id="@+id/drawer_list"
                android:layout_width="240dp"
                android:layout_height="0dip"
                android:choiceMode="singleChoice"
                android:divider="@android:color/transparent"
                android:dividerHeight="0dp"
                android:layout_weight="1"
                />
    </LinearLayout>

</android.support.v4.widget.DrawerLayout>

Activity:

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

    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
    mDrawer = findViewById(R.id.drawer);
    mDrawerList = (ListView) findViewById(R.id.drawer_list);

    mDrawerList.setAdapter(new ArrayAdapter<String>(this,
            R.layout.drawer_list_item, Preferences.getKnownCollections()));
    mDrawerList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapter, View view, int pos, long id) {
                Preferences.setActiveCollection(Preferences.getKnownCollections()[pos]);
                loader.loadAll(Preferences.getKnownCollections()[pos], BrowseActivity.this);
                mDrawerLayout.closeDrawers();
            }
    });

    DrawerHandle.attach(mDrawer, R.layout.handle, 0.2f);

}