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      1 /*
      2  * Copyright (C) 2014 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.camera.widget;
     18 
     19 import android.content.Context;
     20 import android.graphics.Canvas;
     21 import android.util.AttributeSet;
     22 import android.view.View;
     23 import android.widget.TextView;
     24 
     25 /**
     26  * This class defines a generic cling that provides on-screen instructions. A convenient
     27  * method is provided here to automatically adjust the position of the cling to
     28  * always be consistent with the reference view. The use of the convenient method
     29  * is optional.
     30  */
     31 public class Cling extends TextView {
     32 
     33     private View mReferenceView = null;
     34     private final int[] mLocation = new int[2];
     35     private final OnLayoutChangeListener mLayoutChangeListener =
     36             new OnLayoutChangeListener() {
     37                 @Override
     38                 public void onLayoutChange(View v, int left, int top, int right, int bottom,
     39                         int oldLeft, int oldTop, int oldRight, int oldBottom) {
     40                     mDelayDrawingUntilNextLayout = false;
     41                     // Reference view has changed layout.
     42                     adjustPosition();
     43                 }
     44             };
     45     private boolean mDelayDrawingUntilNextLayout = false;
     46 
     47     public Cling(Context context, AttributeSet attrs) {
     48         super(context, attrs);
     49     }
     50 
     51     public Cling(Context context) {
     52         super(context);
     53     }
     54 
     55     /**
     56      * Layout on top of a reference view.
     57      */
     58     public void setReferenceView(View v) {
     59         if (v == null) {
     60             if (mReferenceView != null) {
     61                 // Clear up existing listeners
     62                 mReferenceView.removeOnLayoutChangeListener(mLayoutChangeListener);
     63                 mReferenceView = null;
     64             }
     65             return;
     66         }
     67         mReferenceView = v;
     68         mReferenceView.addOnLayoutChangeListener(mLayoutChangeListener);
     69         if (mReferenceView.getVisibility() == GONE) {
     70             mDelayDrawingUntilNextLayout = true;
     71         } else {
     72             adjustPosition();
     73         }
     74     }
     75 
     76     /**
     77      * Adjust the translation of the cling to stay on top of the reference view.
     78      */
     79     public void adjustPosition() {
     80         if (mReferenceView == null) {
     81             return;
     82         }
     83         mReferenceView.getLocationInWindow(mLocation);
     84         int refCenterX = mLocation[0] + mReferenceView.getWidth() / 2;
     85         int refTopY = mLocation[1];
     86         // Align center with the reference view and move on top
     87         int left = refCenterX - getWidth() / 2;
     88         int top = refTopY - getHeight();
     89 
     90         getLocationInWindow(mLocation);
     91         int currentLeft = mLocation[0] - (int) getTranslationX();
     92         int currentTop = mLocation[1] - (int) getTranslationY();
     93 
     94         setTranslationX(left - currentLeft);
     95         setTranslationY(top - currentTop);
     96     }
     97 
     98     @Override
     99     public void draw(Canvas canvas) {
    100         if (mDelayDrawingUntilNextLayout) {
    101             return;
    102         }
    103         super.draw(canvas);
    104     }
    105 }
    106