Android ApiDemos/ScrollView2 添加自动滚动和智能焦点切换
首先总结一下andorid view的键盘事件处理过程：键盘事件首先交给当前Activity中获得焦点的View，该View的setKeyListener(OnKeyListener l)中设定的l的onKey方法被调用,若返回true,framwork不再处理,否则有framework继续处理.我就是用该方法实现的智能焦点切换。
然后是自动滚动的实现，当ViewGroup中添加了新的View后,不能马上进行滚动,因为此时相应的高度信息还没有更新,需要用Handler来向消息队列投递一个Runnale来进行滚动。
相关实现如下:
1.ScrollView2.java
package com.google.android.samples.view;import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.util.Log;import android.view.KeyEvent;import android.view.View;import android.widget.Button;import android.widget.LinearLayout;import android.widget.ScrollView;import android.widget.TextView;import com.google.android.samples.R;/** * Demonstrates wrapping a layout in a ScrollView. * */public class ScrollView2 extends Activity {private static final String LOG_TAG = "ScrollView2";private LinearLayout mLayout;private ScrollView mScrollView;private final Handler mHandler = new Handler(); @Override protected void onCreate(Bundle icicle) {super.onCreate(icicle);setContentView(R.layout.scroll_view_2);mLayout = (LinearLayout) findViewById(R.id.layout);mScrollView = (ScrollView) findViewById(R.id.scrollview);Button button = (Button) findViewById(R.id.add_widget);button.setOnClickListener(mClickListener);//改变默认焦点切换button.setKeyListener(mAddButtonKeyListener); } private Button.OnClickListener mClickListener = new Button.OnClickListener() { private int mIndex = 1;@Overridepublic void onClick(View arg0) {// TODO Auto-generated method stub TextView textView = new TextView(ScrollView2.this); textView.setText("Text View " + mIndex); LinearLayout.LayoutParams p = new LinearLayout.LayoutParams( LinearLayout.LayoutParams.FILL_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT ); mLayout.addView(textView, p); Button buttonView = new Button(ScrollView2.this); buttonView.setText("Button " + mIndex++); mLayout.addView(buttonView, p); //改变默认焦点切换 buttonView.setKeyListener(mNewButtonKeyListener); //投递一个消息进行滚动 mHandler.post(mScrollToBottom);} }; private Runnable mScrollToBottom = new Runnable() {@Overridepublic void run() {// TODO Auto-generated method stubLog.d(LOG_TAG, "ScrollY: " + mScrollView.getScrollY()); int off = mLayout.getMeasuredHeight() - mScrollView.getHeight(); if (off > 0) { mScrollView.scrollTo(0, off); }} }; private View.OnKeyListener mNewButtonKeyListener = new View.OnKeyListener() { public boolean onKey(View v, int keyCode, KeyEvent event) { if (keyCode == KeyEvent.KEYCODE_DPAD_DOWN && event.getAction() == KeyEvent.ACTION_DOWN && v == mLayout.getChildAt(mLayout.getChildCount() - 1)) { findViewById(R.id.add_widget).requestFocus(); return true; } return false; } }; private View.OnKeyListener mAddButtonKeyListener = new Button.OnKeyListener() {@Overridepublic boolean onKey(View v, int keyCode, KeyEvent event) {// TODO Auto-generated method stubLog.d(LOG_TAG, event.toString());View viewToFoucus = null;if (event.getAction() == KeyEvent.ACTION_DOWN) {switch (keyCode) {case KeyEvent.KEYCODE_DPAD_UP:int iCount = mLayout.getChildCount();if ( iCount > 0) {viewToFoucus = mLayout.getChildAt(iCount - 1);}break;case KeyEvent.KEYCODE_DPAD_DOWN:if (mLayout.getChildCount() > 1) {viewToFoucus = mLayout.getChildAt(1);}break;default:break;}}if (viewToFoucus != null) {viewToFoucus.requestFocus();return true;} else {return false;}}};}
2.scroll_view_2.xml
<?xml version="1.0" encoding="utf-8"?><!-- Demonstrates scrolling with a ScrollView. --><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="fill_parent"android:layout_height="wrap_content"android:orientation="vertical"><Button id="@+id/add_widget"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Add Widget"/><ScrollView id="@+id/scrollview" android:layout_width="fill_parent" android:layout_height="wrap_content" android:scrollbars="vertical"> <LinearLayout id="@+id/layout" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="wrap_content"> </LinearLayout></ScrollView></LinearLayout>
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