Android View中的setMeasuredDimension方法

继承View,实现自己想要的组件,那么需要使用到setMeasuredDimension这个方法,这个方法决定了当前View的大小,请看代码:View的代码:

package cc.mdev.test;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.text.TextPaint;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;

public class MyScrollView extends View {

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

public MyScrollView(Context context) {
super(context);
}
@Override
protected void onDraw(Canvas canvas) {
TextPaint paint = new TextPaint();
paint.setAntiAlias(true);
canvas.drawColor(Color.GRAY);
for (int i = 10; i < 500; i++) {
canvas.drawText("This is the scroll text.", 10, i, paint);
i = i+15;
}
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
String tag="onMeasure";
Log.e(tag, "Scroll View on measure...");
setMeasuredDimension(200, 800);
}

@Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
String tag = "onScrollChanged";
Log.e(tag, "Scroll....");
super.onScrollChanged(l, t, oldl, oldt);
}
}
 

布局文件:

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="#fff" > <Button android:text="Button01" android:id="@+id/Button01" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button> <ScrollView android:layout_width="fill_parent" android:layout_height="fill_parent"> <cc.mdev.test.MyScrollView android:layout_width="wrap_content" android:layout_height="wrap_content"/> </ScrollView> </LinearLayout>
 

效果就是自定义视图的大小为

200,800,并且放入到ScrollView中,ScrollView会启作用,如果不使用setMeasuredDimension这个方法,那么

ScrollView不会有作用。

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