Android获取Android控件的宽和高

我们都知道在onCreate()里面获取控件的高度是0,这是为什么呢?我们来看一下示例:

首先我们自己写一个控件,这个控件非常简单:

public class MyImageViewextends ImageView {

    public MyImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
    public MyImageView(Context context) {
        super(context);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec,int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        System.out.println("onMeasure 我被调用了"+System.currentTimeMillis());
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        System.out.println("onDraw 我被调用了"+System.currentTimeMillis());
    }

}

public class MyImageView extends ImageView {

	public MyImageView(Context context, AttributeSet attrs) {
		super(context, attrs);
	}
	public MyImageView(Context context) {
		super(context);
	}
	
	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		System.out.println("onMeasure 我被调用了"+System.currentTimeMillis());
	}
	
	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);
		System.out.println("onDraw 我被调用了"+System.currentTimeMillis());
	}

}

布局文件:

<com.test.MyImageView
    android:id="@+id/imageview"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/test" />

    <com.test.MyImageView
        android:id="@+id/imageview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/test" />

测试的Activity的onCreate():

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    System.out.println("执行完毕.."+System.currentTimeMillis());
}

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);        
        System.out.println("执行完毕.."+System.currentTimeMillis());
    }

现在我们现在来看一下结果:

说明等onCreate方法执行完了,我们定义的控件才会被度量(measure),所以我们在onCreate方法里面通过view.getHeight()获取控件的高度或者宽度肯定是0,因为它自己还没有被度量,也就是说他自己都不知道自己有多高,而你这时候去获取它的尺寸,肯定是不行的.

现在碰到这个问题我们不能不解决,在网上找到了如下办法:

//------------------------------------------------方法一
int w = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
int h = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
imageView.measure(w, h);
int height =imageView.getMeasuredHeight();
int width =imageView.getMeasuredWidth();
textView.append("\n"+height+","+width);




//-----------------------------------------------方法二
ViewTreeObserver vto = imageView.getViewTreeObserver();
vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
    public boolean onPreDraw() {
        int height = imageView.getMeasuredHeight();
        int width = imageView.getMeasuredWidth();
        textView.append("\n"+height+","+width);
        return true;
    }
});
//-----------------------------------------------方法三
ViewTreeObserver vto2 = imageView.getViewTreeObserver();
vto2.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
    @Override
    public void onGlobalLayout() {
        imageView.getViewTreeObserver().removeGlobalOnLayoutListener(this);
        textView.append("\n\n"+imageView.getHeight()+","+imageView.getWidth());
    }
});

        //------------------------------------------------方法一
        int w = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
        int h = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
        imageView.measure(w, h);
        int height =imageView.getMeasuredHeight();
        int width =imageView.getMeasuredWidth();
        textView.append("\n"+height+","+width);
        
        
        

        //-----------------------------------------------方法二
        ViewTreeObserver vto = imageView.getViewTreeObserver();
        vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
            public boolean onPreDraw() {
                int height = imageView.getMeasuredHeight();
                int width = imageView.getMeasuredWidth();
                textView.append("\n"+height+","+width);
                return true;
            }
        });
        //-----------------------------------------------方法三   
        ViewTreeObserver vto2 = imageView.getViewTreeObserver();  
        vto2.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
            @Override  
            public void onGlobalLayout() {
            	imageView.getViewTreeObserver().removeGlobalOnLayoutListener(this);  
                textView.append("\n\n"+imageView.getHeight()+","+imageView.getWidth());
            }  
        });  

这三个方法是哪里找到现在已经忘了.

现在要讨论的是当我们需要时候使用哪个方法呢?

现在把测试的Activity改成如下:

@Override
  public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.main);
      final ImageView imageView = (ImageView) findViewById(R.id.imageview);

      //------------------------------------------------方法一
      int w = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
      int h = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
      imageView.measure(w, h);
      int height =imageView.getMeasuredHeight();
      int width =imageView.getMeasuredWidth();
      textView.append("\n"+height+","+width);

      System.out.println("执行完毕.."+System.currentTimeMillis());
  }

  @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        final ImageView imageView = (ImageView) findViewById(R.id.imageview);      
        
        //------------------------------------------------方法一
        int w = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
        int h = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
        imageView.measure(w, h);
        int height =imageView.getMeasuredHeight();
        int width =imageView.getMeasuredWidth();
        textView.append("\n"+height+","+width);
        
        System.out.println("执行完毕.."+System.currentTimeMillis());
    }

接着来看下面几种方式输出结果:

把测试Activity改成如下:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    final ImageView imageView = (ImageView) findViewById(R.id.imageview);
-----------------------------------------------方法二
    ViewTreeObserver vto = imageView.getViewTreeObserver();
    vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
        public boolean onPreDraw() {
            int height = imageView.getMeasuredHeight();
            int width = imageView.getMeasuredWidth();
            textView.append("\n"+height+","+width);
            return  true;
        }
    });
}

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        final ImageView imageView = (ImageView) findViewById(R.id.imageview);
		//-----------------------------------------------方法二
        ViewTreeObserver vto = imageView.getViewTreeObserver();
        vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
            public boolean onPreDraw() {
                int height = imageView.getMeasuredHeight();
                int width = imageView.getMeasuredWidth();
                textView.append("\n"+height+","+width);
                return true;
            }
        });
    }

结果如下:

方法三就不再测试了同方法二!!!

那么方法而和方法三在执行上有什么区别呢?

我们在布局文件中加入一个TextView来记录这个控件的宽高.

<ScrollView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" >

    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</ScrollView>

    <ScrollView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" >

        <TextView
            android:id="@+id/text"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
    </ScrollView>

先来测试方法而:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    final ImageView imageView = (ImageView) findViewById(R.id.imageview);
-----------------------------------------------方法二
    ViewTreeObserver vto = imageView.getViewTreeObserver();
    vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
        public boolean onPreDraw() {
            int height = imageView.getMeasuredHeight();
            int width = imageView.getMeasuredWidth();
            textView.append("\n"+height+","+width);
            return  true;
        }
    });
}

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        final ImageView imageView = (ImageView) findViewById(R.id.imageview);
		//-----------------------------------------------方法二
        ViewTreeObserver vto = imageView.getViewTreeObserver();
        vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
            public boolean onPreDraw() {
                int height = imageView.getMeasuredHeight();
                int width = imageView.getMeasuredWidth();
                textView.append("\n"+height+","+width);
                return true;
            }
        });
    }

结果如下:

我们再来测试方法三

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    final ImageView imageView = (ImageView) findViewById(R.id.imageview);
    //-----------------------------------------------方法三
    ViewTreeObserver vto2 = imageView.getViewTreeObserver();
    vto2.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
        @Override
        public void onGlobalLayout() {
            imageView.getViewTreeObserver().removeGlobalOnLayoutListener(this);
            textView.append("\n\n"+imageView.getHeight()+","+imageView.getWidth());
        }
    });
}

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        final ImageView imageView = (ImageView) findViewById(R.id.imageview);
        //-----------------------------------------------方法三   
        ViewTreeObserver vto2 = imageView.getViewTreeObserver();  
        vto2.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
            @Override  
            public void onGlobalLayout() {
            	imageView.getViewTreeObserver().removeGlobalOnLayoutListener(this);  
                textView.append("\n\n"+imageView.getHeight()+","+imageView.getWidth());
            }  
        });  
    }

输出结果如下:

我想这方法二和方法三之间的区别就不用说了吧.

总结:那么需要获取控件的宽高该用那个方法呢?

方法一: 比其他的两个方法多了一次计算,也就是多调用了一次onMeasure()方法,该方法虽然看上去简单,但是如果要目标控件计算耗时比较大的话(如listView等),不建议使用.

方法二,它的回调方法会调用很多次,并且滑动TextView的时候任然会调用,所以不建议使用.

方法三,比较合适.

当然,实际应用的时候需要根据实际情况而定.

转载于：:http://blog.csdn.net/johnny901114/article/details/7839512