Android 執行個體-個人財務工具 之一 啟動介面實現

轉　：　http://hi.baidu.com/android%5Ffans/blog/item/299c0dfa37a60c116c22eb33.html啟動介面的主要功能就是顯示一幅啟動映像,後台進行系統初始化.如果是第一次使用本程式,需要初始化本程式的sqlite資料庫,建庫,建Table,初始化賬目資料.如果不是第一次使用,就進入登記收支記錄介面.

介面效果:

介面很簡單,一個imageview 和一個textview可是如何是2個view 垂直置中顯示,我開始使用linearlayout就沒法完成垂直和橫向置中.後來使用RelativeLayout 才搞定了橫向置中.介面的具體xml如下:main.xml

1. <?xml version="1.0" encoding="utf-8"?>
2. <RelativeLayout android:id="@+id/RelativeLayout01" xmlns:android="http://schemas.android.com/apk/res/android"
3. android:layout_gravity="center_vertical|center_horizontal"
4. android:layout_height="wrap_content"
5. android:layout_width="wrap_content">
6. <ImageView android:id="@+id/ImageView01"
7. android:src="@drawable/logo3"
8. android:layout_width="wrap_content"
9. android:layout_height="wrap_content">
10. </ImageView>
11. <TextView android:id="@+id/TextView01"
12. android:text="@string/welcome"
13. android:layout_below="@id/ImageView01"
14. android:layout_width="wrap_content"
15. android:layout_height="wrap_content">
16. </TextView>
17. </RelativeLayout>

在這兒我來使用一個小技巧,就是在程式初始化完成後,讓圖片淡出,然後顯示下一個介面.

開始我準備使用一個timer來更新圖片的alpha值,後來程式拋出異常Only the original thread that created a view hierarchy can touch its views.這才發現android 的ui 控制項是安全執行緒的.這裡需要我們在主線程外,再開一個線程更新介面上的圖片.可以使用imageview.invalidate關於如何另開一個線程更新介面的相關代碼如下.

1. //給主線程發送訊息更新imageview
2. mHandler = new Handler() {
3. @Override
4. public void handleMessage(Message msg) {
5. super.handleMessage(msg);
6. imageview.setAlpha(alpha);
7. imageview.invalidate();
8. }
9. };
10. new Thread(new Runnable() {
11. public void run() {
12. while (b < 2) {
13. try {
14. //延時2秒後,每50毫秒更新一次imageview
15. if (b == 0) {
16. Thread.sleep(2000);
17. b = 1;
18. } else {
19. Thread.sleep(50);
20. }
21. updateApp();
22. } catch (InterruptedException e) {
23. e.printStackTrace();
24. }
25. }
26. }
27. }).start();
28. public void updateApp() {
29. alpha -= 5;//每次減少alpha 5
30. if (alpha <= 0) {
31. b = 2;
32. Intent in = new Intent(this, com.cola.ui.Frm_Addbills.class);
33. startActivity(in);//啟動下個介面
34. }
35. mHandler.sendMessage(mHandler.obtainMessage());
36. }

 

通過這段代碼,我們能夠理解android 裡面如何對ui視圖進行更新.

下篇文章我們來看看sqlite的使用.如何初始化程式.

關於handler,invalidate 的用法,

大家還可以參考這篇文章.http://www.blogjava.net/gooogle/archive/2008/03/05/184030.html

 

附ColaBox.java:

1. package com.cola.ui;
2. import android.app.Activity;
3. import android.content.Intent;
4. import android.os.Bundle;
5. import android.os.Handler;
6. import android.os.Message;
7. import android.util.Log;
8. import android.view.KeyEvent;
9. import android.widget.ImageView;
10. import android.widget.TextView;
11. public class ColaBox extends Activity {
12.     private Handler mHandler = new Handler();
13.      ImageView imageview;
14.      TextView textview;
15.     int alpha = 255;
16.     int b = 0;
17.     public void onCreate(Bundle savedInstanceState) {
18.         super.onCreate(savedInstanceState);
19.          setContentView(R.layout.main);
20.          imageview = (ImageView) this.findViewById(R.id.ImageView01);
21.          textview = (TextView) this.findViewById(R.id.TextView01);
22.          Log.v("ColaBox", "ColaBox start ...");
23.          imageview.setAlpha(alpha);
24.         new Thread(new Runnable() {
25.             public void run() {
26.                  initApp(); //初始化程式
27.                 
28.                 while (b < 2) {
29.                     try {
30.                         if (b == 0) {
31.                              Thread.sleep(2000);
32.                              b = 1;
33.                          } else {
34.                              Thread.sleep(50);
35.                          }
36.                          updateApp();
37.                      } catch (InterruptedException e) {
38.                          e.printStackTrace();
39.                      }
40.                  }
41.              }
42.          }).start();
43.          mHandler = new Handler() {
44.             @Override
45.             public void handleMessage(Message msg) {
46.                 super.handleMessage(msg);
47.                  imageview.setAlpha(alpha);
48.                  imageview.invalidate();
49.              }
50.          };
51.      }
52.     public void updateApp() {
53.          alpha -= 5;
54.         if (alpha <= 0) {
55.              b = 2;
56.              Intent in = new Intent(this, com.cola.ui.Frm_Addbills.class);
57.              startActivity(in);
58.          }
59.          mHandler.sendMessage(mHandler.obtainMessage());
60.      }
61.     
62.     public void initApp(){
63.         
64.      }
65. }