Question

应用程序运行。它应该做的是在文本框中显示“= Heightofthescreen =”，其中Heightofthescreen是屏幕的实际值。相反，它只是给了我一个0.我想它是我的背景，但我不知道如何解决它。

活动类：

package com.example.measuringtesting;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

public class StartDraw extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        Drawing.context2 = getApplicationContext();
        Drawing y = new Drawing(Drawing.context2);
        int theheight = y.width2;
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_start_draw);
        TextView t = new TextView(this); 

        t=(TextView)findViewById(R.id.textView1); 
        t.setText("=" + theheight + "=");
    }
}

这是视图类：

package com.example.measuringtesting;

import android.content.Context;
import android.view.View;

public class Drawing extends View {
public Drawing(Context context) {
    super(context);
}

public float width;
public float height;
public int width2;
public int height2;
public static Context context2;

@Override 
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){
float parentWidth = MeasureSpec.getSize(widthMeasureSpec);
float parentHeight = MeasureSpec.getSize(heightMeasureSpec);
this.width = (float) (parentWidth*.15);
this.height = (float) (parentHeight*.15);
this.width2 = Math.round(width);
this.height2 = Math.round(height);
this.setMeasuredDimension(width2, height2);
}

}

Answer 1

问题是在绘制布局之前不会调用onMeasure()，这比在TextView中设置文本的时间晚一些。所以现在y.width2仍然是0.

看看这个问题：When Can I First Measure a View?

基本上，您必须将GlobalLayoutListener添加到要测量的视图的ViewTreeObserver。您可以在public void onGlobalLayout()的{{1}}回调中找到您的观看次数。

onMeasure from View在我的活动中产生0

1 个答案: