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Android学习Scroller(二)
MainActivity如下:
package cc.testscroller1;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.LinearLayout.LayoutParams;
import android.widget.Scroller;
/**
* Demo描述:
* 学习Scroller类(原理篇)
*
* 原理分析:
* 点击Button的背景将发生变化,这时button将调用invalidate()请求重绘,
* 这就是View系统重绘的源头,即scroll动态效果的触发者.
* 既然重绘请求已发出,那么整个View系统就会进行一次自上而下的绘制.
* 所以先OuterLinearLayout重绘,然后InnerLinearLayout,最后是自定义的Button.
* 但在InnerLinearLayout中又执行了scrollTo(),这会导致Button的重绘.
* 于是又开始至上而下的重绘,该过程会一直进行下去,直到mScroller.computeScrollOffset()
* 返回false.
*
*
* 测试说明:
* 测试时可分别注释掉第149和185行观察效果
*
*
* 备注说明:
* 1 关于方法startScroll(int startX, int startY, int dx, int dy, int duration)
* 第一个参数:开始滑动的X位置
* 第二个参数:开始滑动的Y位置
* 第三个参数:X方向滑动的距离,正数向左,负数向右
* 第四个参数:Y方向滑动的距离,正数向上,负数向下
* 第五个参数:滑动持续的时间
*
* 该方法只是一个Scroll的行为模型(见参考资料6).它只是为Scroll这个行为设置了一些
* 属性而已.有时看到这个方法的名字startScroll()以为它就是用来控制和启动滑动.
* 其实不是的,真正用来滑动的是下面这个方法scrollTo(int x, int y).
* 虽然它不是用来实际滑动的,但是可以在其它地方取得该方法中设置的这些属性.
* 比如 mScroller.getCurrX()或者mScroller.getDuration()等等
*
* 2 关于方法scrollTo(int x, int y)
* Set the scrolled position of your view
* 它才是将View滑动到指定的位置进行显示
*
* 3 关于方法computeScrollOffset()
* If it returns true, the animation is not yet finished.
* 返回值为boolean类型true说明滚动尚未完成,false说明滚动已完成
* 该方法通常放在computeScroll()中用来判断是否滚动是否结束
*
*
* 参考资料:
* 1 http://blog.csdn.net/gemmem/article/details/7321910
* 2 http://gundumw100.iteye.com/blog/1884373
* 3 http://ipjmc.iteye.com/blog/1615828
* 4 http://blog.csdn.net/c_weibin/article/details/7438323
* 5 http://www.cnblogs.com/wanqieddy/archive/2012/05/05/2484534.html
* 6 http://blog.csdn.net/hudashi/article/details/7353075
*
* Thank you very much
*/
public class MainActivity extends Activity {
private OuterLinearLayout mOuterLinearLayout;
private InnerLinearLayout mInnerLinearLayout1;
private InnerLinearLayout mInnerLinearLayout2;
private Scroller mScroller;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mScroller = new Scroller(this);
//OuterLinearLayout是最外层的LinearLayout
mOuterLinearLayout = new OuterLinearLayout(this);
mOuterLinearLayout.setOrientation(LinearLayout.VERTICAL);
LayoutParams outerLinearLayoutLayoutParams =
new LayoutParams(LayoutParams.FILL_PARENT,LayoutParams.FILL_PARENT);
this.setContentView(mOuterLinearLayout, outerLinearLayoutLayoutParams);
//InnerLinearLayout内层的第一个LinearLayout
mInnerLinearLayout1 = new InnerLinearLayout(this);
mInnerLinearLayout1.setBackgroundColor(Color.parseColor("#ff0033"));
LayoutParams innerLinearLayoutLayoutParams1 =
new LayoutParams(LayoutParams.FILL_PARENT,LayoutParams.FILL_PARENT);
innerLinearLayoutLayoutParams1.weight=1;
mOuterLinearLayout.addView(mInnerLinearLayout1,innerLinearLayoutLayoutParams1);
//InnerLinearLayout内层的第二个LinearLayout
mInnerLinearLayout2 = new InnerLinearLayout(this);
mInnerLinearLayout2.setBackgroundColor(Color.parseColor("#0000cc"));
LayoutParams innerLinearLayoutLayoutParams2 =
new LayoutParams(LayoutParams.FILL_PARENT,LayoutParams.FILL_PARENT);
innerLinearLayoutLayoutParams2.weight=1;
mOuterLinearLayout.addView(mInnerLinearLayout2,innerLinearLayoutLayoutParams2);
//为第一个LinearLayout添加一个Button
ButtonSubClass buttonSubClass1 = new ButtonSubClass(this);
buttonSubClass1.setText("Button1 in LinearLayout1");
buttonSubClass1.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
//参见上方的备注说明1
mScroller.startScroll(20, 20, -200, -200, 1000);
}
});
mInnerLinearLayout1.addView(buttonSubClass1);
//为第二个LinearLayout添加一个Button
ButtonSubClass buttonSubClass2 = new ButtonSubClass(this);
buttonSubClass2.setText("Button2 in LinearLayout2");
buttonSubClass2.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
//参见上方的备注说明1
mScroller.startScroll(20, 20, -200, -200, 1000);
}
});
mInnerLinearLayout2.addView(buttonSubClass2);
}
class OuterLinearLayout extends LinearLayout {
public OuterLinearLayout(Context context) {
super(context);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
System.out.println("OuterLinearLayout---> onDraw()");
}
@Override
public void computeScroll() {
//参见上方的备注说明3
if (mScroller.computeScrollOffset()){
//参见上方的备注说明2
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
System.out.println("OuterLinearLayout---> computeScroll()");
//System.out.println("InnerLinearLayout computeScroll()---> CurrX()="
// +mScroller.getCurrX()+",CurrY="+mScroller.getCurrY()+
// ",StartX()="+mScroller.getStartX()+",StartY="+mScroller.getStartY());
}
}
@Override
protected void dispatchDraw(Canvas canvas) {
super.dispatchDraw(canvas);
System.out.println("OuterLinearLayout --->dispatchDraw()");
}
}
class InnerLinearLayout extends LinearLayout {
public InnerLinearLayout(Context context) {
super(context);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
System.out.println("InnerLinearLayout---> onDraw()");
}
@Override
public void computeScroll() {
//参见上方的备注说明3
if (mScroller.computeScrollOffset()){
//参见上方的备注说明2
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
System.out.println("InnerLinearLayout---> computeScroll()");
//System.out.println("InnerLinearLayout computeScroll()---> CurrX()="
// +mScroller.getCurrX()+",CurrY="+mScroller.getCurrY()+
// ",StartX()="+mScroller.getStartX()+",StartY="+mScroller.getStartY());
}
}
}
class ButtonSubClass extends Button {
public ButtonSubClass(Context context) {
super(context);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
System.out.println("ButtonSubClass---> onDraw()");
}
}
}main.xml如下:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</RelativeLayout>
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