Android添加自动滚动和智能焦点切换

第一种方法:

把布局放到scrollView中,让要显示的View(隐藏的View滚动出来)获取焦点,View会自动滚动出来.

第二种方法:

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 
代码:

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;   
        @Override  
        public 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() {   
        @Override  
        public void run() {   
            // TODO Auto-generated method stub   
            Log.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() {   
        @Override  
        public boolean onKey(View v, int keyCode, KeyEvent event) {   
            // TODO Auto-generated method stub   
            Log.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

代码:

<?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>