android 滚动视图（ScrollView）学习与应用

文章转自：http://www.javaeye.com/topic/149773

[c-sharp] view plain copy print ?

1. import android.app.Activity;    
2. import android.os.Bundle;    
3. import android.os.Handler;    
4. import android.util.Log;    
5. import android.view.KeyEvent;    
6. import android.view.View;    
7. import android.widget.Button;    
8. import android.widget.LinearLayout;    
9. import android.widget.ScrollView;    
10. import android.widget.TextView;    
11. import com.scrollview.R;  
12. /** 
13. * Demonstrates wrapping a layout in a ScrollView. 
14. * 
15. */   
16. public class Scrollview extends Activity {    
17.     private static final String LOG_TAG = "Scrollview";    
18.     private LinearLayout mLayout;    
19.     private ScrollView mScrollView;    
20.     private final Handler mHandler = new Handler();    
21.         
22.     @Override   
23.     protected void onCreate(Bundle icicle) {    
24.         super.onCreate(icicle);    
25.         setContentView(R.layout.main);    
26.    
27.         mLayout = (LinearLayout) findViewById(R.id.layout);    
28.         mScrollView = (ScrollView) findViewById(R.id.scrollview);    
29.    
30.         Button button = (Button) findViewById(R.id.add_widget);    
31.         button.setOnClickListener(mClickListener);    
32.         //改变默认焦点切换    
33.         button.setOnKeyListener(mAddButtonKeyListener);    
34.     }    
35.         
36.     private Button.OnClickListener mClickListener = new Button.OnClickListener() {    
37.         private int mIndex = 1;    
38.         @Override   
39.         public void onClick(View arg0) {    
40.             // TODO Auto-generated method stub         
41.             TextView textView = new TextView(Scrollview.this);    
42.             textView.setText("Text View " + mIndex);    
43.             LinearLayout.LayoutParams p = new LinearLayout.LayoutParams(    
44.                     LinearLayout.LayoutParams.FILL_PARENT,    
45.                     LinearLayout.LayoutParams.WRAP_CONTENT    
46.             );    
47.             mLayout.addView(textView, p);    
48.    
49.             Button buttonView = new Button(Scrollview.this);    
50.             buttonView.setText("Button " + mIndex++);    
51.             mLayout.addView(buttonView, p);    
52.             //改变默认焦点切换    
53.             buttonView.setOnKeyListener(mNewButtonKeyListener);    
54.             //投递一个消息进行滚动    
55.             mHandler.post(mScrollToBottom);    
56.         }           
57.     };    
58.         
59.     private Runnable mScrollToBottom = new Runnable() {    
60.         @Override   
61.         public void run() {    
62.             // TODO Auto-generated method stub    
63.             Log.d(LOG_TAG, "ScrollY: " + mScrollView.getScrollY());    
64.             int off = mLayout.getMeasuredHeight() - mScrollView.getHeight();    
65.             if (off > 0) {    
66.                 mScrollView.scrollTo(0, off);    
67.             }                           
68.         }    
69.     };    
70.        
71.     private View.OnKeyListener mNewButtonKeyListener = new View.OnKeyListener() {    
72.         public boolean onKey(View v, int keyCode, KeyEvent event) {    
73.             if (keyCode == KeyEvent.KEYCODE_DPAD_DOWN &&    
74.                     event.getAction() == KeyEvent.ACTION_DOWN &&    
75.                     v == mLayout.getChildAt(mLayout.getChildCount() - 1)) {    
76.                 findViewById(R.id.add_widget).requestFocus();    
77.                 return true;    
78.             }    
79.             return false;    
80.         }    
81.     };    
82.         
83.     private View.OnKeyListener mAddButtonKeyListener = new Button.OnKeyListener() {    
84.         @Override   
85.         public boolean onKey(View v, int keyCode, KeyEvent event) {    
86.             // TODO Auto-generated method stub    
87.             Log.d(LOG_TAG, event.toString());    
88.                 
89.             View viewToFoucus = null;    
90.             if (event.getAction() == KeyEvent.ACTION_DOWN) {    
91.                 switch (keyCode) {    
92.                 case KeyEvent.KEYCODE_DPAD_UP:    
93.                     int iCount = mLayout.getChildCount();    
94.                     if ( iCount > 0) {    
95.                         viewToFoucus = mLayout.getChildAt(iCount - 1);    
96.                     }    
97.                     break;    
98.                 case KeyEvent.KEYCODE_DPAD_DOWN:    
99.                     if (mLayout.getChildCount() > 1) {    
100.                         viewToFoucus = mLayout.getChildAt(1);    
101.                     }    
102.                     break;    
103.                 default:    
104.                     break;    
105.                 }    
106.             }    
107.                 
108.             if (viewToFoucus != null) {    
109.                 viewToFoucus.requestFocus();    
110.                 return true;    
111.             } else {    
112.                 return false;    
113.             }    
114.         }    
115.     };    
116. }   

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.scrollview.R; /** * Demonstrates wrapping a layout in a ScrollView. * */ public class Scrollview extends Activity { private static final String LOG_TAG = "Scrollview"; private LinearLayout mLayout; private ScrollView mScrollView; private final Handler mHandler = new Handler(); @Override protected void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.main); 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.setOnKeyListener(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(Scrollview.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(Scrollview.this); buttonView.setText("Button " + mIndex++); mLayout.addView(buttonView, p); //改变默认焦点切换 buttonView.setOnKeyListener(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; } } }; }

[c-sharp] view plain copy print ?

1. <?xml version="1.0" encoding="utf-8"?>    
2. <!-- Demonstrates scrolling with a ScrollView. -->    
3. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"   
4.     android:layout_width="fill_parent"   
5.     android:layout_height="wrap_content"   
6.     android:orientation="vertical">    
7.     <Button android:id="@+id/add_widget"   
8.         android:layout_width="wrap_content"   
9.         android:layout_height="wrap_content"   
10.         android:text="增加按钮"/>    
11. <ScrollView  
12.     android:id="@+id/scrollview"   
13.     android:layout_width="fill_parent"   
14.     android:layout_height="wrap_content"   
15.     android:scrollbars="vertical">    
16.     <LinearLayout    
17.         android:id="@+id/layout"   
18.         android:orientation="vertical"   
19.         android:layout_width="fill_parent"   
20.         android:layout_height="wrap_content">    
21.     </LinearLayout>    
22. </ScrollView>    
23. </LinearLayout>   

<?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 android:id="@+id/add_widget" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="增加按钮"/> <ScrollView android:id="@+id/scrollview" android:layout_width="fill_parent" android:layout_height="wrap_content" android:scrollbars="vertical"> <LinearLayout android:id="@+id/layout" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="wrap_content"> </LinearLayout> </ScrollView> </LinearLayout>

小结：

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。