Android編程獲取控件寬和高的方法總結分析

2020-04-11 11:02:01

字體：大中小

來源：轉載

供稿：網友

本文總結分析了Android編程獲取控件寬和高的方法。分享給大家供大家參考，具體如下：

我們都知道在onCreate()里面獲取控件的高度是0,這是為什么呢?我們來看一下示例:

首先我們自己寫一個控件,這個控件非常簡單:

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 我被調用了"+System.currentTimeMillis());  }  @Override  protected void onDraw(Canvas canvas) {    super.onDraw(canvas);    System.out.println("onDraw 我被調用了"+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" />

測試的Activity的onCreate():

@Overridepublic void onCreate(Bundle savedInstanceState) {  super.onCreate(savedInstanceState);  setContentView(R.layout.main);  System.out.println("執行完畢.."+System.currentTimeMillis());}

現在我們現在來看一下結果:

說明等onCreate方法執行完了,我們定義的控件才會被度量(measure),所以我們在onCreate方法里面通過view.getHeight()獲取控件的高度或者寬度肯定是0,因為它自己還沒有被度量,也就是說他自己都不知道自己有多高,而你這時候去獲取它的尺寸,肯定是不行的.

現在碰到這個問題我們不能不解決,在網上找到了如下辦法:

//------------------------------------------------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());  }});

這三個方法是哪里找到現在已經忘了.

現在要討論的是當我們需要時候使用哪個方法呢?

現在把測試的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("執行完畢.."+System.currentTimeMillis()); }

接著來看下面幾種方式輸出結果:

把測試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;    }  });}

結果如下:

方法三就不再測試了同方法二!!!

那么方法而和方法三在執行上有什么區別呢?

我們在布局文件中加入一個TextView來記錄這個控件的寬高.

<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>

先來測試方法二:

@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;    }  });}

結果如下:

我們再來測試方法三

@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());    }  });}

輸出結果如下: