Android编程获取控件宽和高的方法总结分析

2020-04-11 11:02:01

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本文总结分析了Android编程获取控件宽和高的方法。分享给大家供大家参考，具体如下：

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 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" />

测试的Activity的onCreate():

@Overridepublic 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());  }});

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()); }

接着来看下面几种方式输出结果:

把测试Activity改成如下:

@Overridepublic 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>

先来测试方法二:

@Overridepublic 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

@Overridepublic 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: