Android零碎知识（一）

public abstract Resources getResources ()

Return a Resources instance for your application's package.

BitmapFactory
extends Object

java.lang.Object
   ↳ android.graphics.BitmapFactory 

Class Overview

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Creates Bitmap objects from various sources, including files, streams, and byte-arrays. 

public void translate (float dx, float dy)
Added in API level 1
Preconcat the current matrix with the specified translation

When working with matrices, the word concatenation refers to multiplication.

Since matrix multiplication is not commutative, there is a separate word for backwards multiplication.
Pre-concatenating a to b means setting a = b × a. (As opposed to a = a × b, which will give a different matrix)

The canvas maintains a matrix and the canvas is manipulated by methods which are well defined in OpenGL

三种列表对话框：setItems，setItems，setMultiChoiceItems。

在 接口DialogInterface.OnClickListener的抽象方法

public abstract void onClick (DialogInterface dialog, int which) 中的参数which：The button that was clicked (e.g. BUTTON1)
or the position of the item clicked

既能监听列表项（>=0）,又能监听按钮（<=0)

BUTTON_NEGATIVE=-2，BUTTON_NEUTRAL=-3，BUTTON_POSITIVE=-1；

public AlertDialog.Builder setSingleChoiceItems (CharSequence[] items, int checkedItem, DialogInterface.OnClickListener listener)

其中参数checkedItem  specifies which item is checked. If -1 no items are checked.因为有默认选项，onclick方法若不点击列表项，这个默认值就获取不到，所以在onclick方法里需要设置index的默认值为1。下面的程序是在构造方法传入1的。

另外注意在多选列表对话框中是如何获得用户选择的列表项，先得到对话框的Listview对象，扫描的方式

 

 package net.blogjava.mobile;

 import android.app.Activity;
 import android.app.AlertDialog;
 import android.content.DialogInterface;
 import android.os.Bundle;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.ListView;

 public class Main extends Activity implements OnClickListener
 {
     private String[] provinces = new String[]
     { "辽宁省", "山东省", "河北省", "福建省", "广东省", "黑龙江省" };
     private ButtonOnClick buttonOnClick = new ButtonOnClick(1);
     private ListView lv = null;
     private void showListDialog()
     {
         new AlertDialog.Builder(this).setTitle("选择省份").setItems(provinces,
                 new DialogInterface.OnClickListener()
                 {
                     public void onClick(DialogInterface dialog, int which)
                     {
                         final AlertDialog ad = new AlertDialog.Builder(
                                 Main.this).setMessage(
                                 "您已经选择了: " + which + ":" + provinces[which])
                                 .show();
                         android.os.Handler hander = new android.os.Handler();
                         hander.postDelayed(new Runnable()
                         {
                             @Override
                             public void run()
                             {
                                 ad.dismiss();

                             }
                         }, 5 * 1000);

                     }
                 }).show();
     }

     private void showSingleChoiceDialog()
     {

         new AlertDialog.Builder(this).setTitle("选择省份").setSingleChoiceItems(
                 provinces, 1, buttonOnClick).setPositiveButton("确定",
                 buttonOnClick).setNegativeButton("取消", buttonOnClick).show();

     }

     private void showMultiChoiceDialog()
     {

         AlertDialog ad = new AlertDialog.Builder(this)
                 .setIcon(R.drawable.image).setTitle("选择省份")
                 .setMultiChoiceItems(provinces, new boolean[]
                 { false, true, false, true, false, false },
                         new DialogInterface.OnMultiChoiceClickListener()
                         {
                             public void onClick(DialogInterface dialog,
                                     int whichButton, boolean isChecked)
                             {

                             }
                         }).setPositiveButton("确定",
                         new DialogInterface.OnClickListener()
                         {
                             public void onClick(DialogInterface dialog,
                                     int whichButton)
                             {
                                 int count = lv.getCount();
                                 String s = "您选择了:";
                                 for (int i = 0; i < provinces.length; i++)
                                 {

                                     if (lv.getCheckedItemPositions().get(i))
                                         s += i + ":"
                                                 + lv.getAdapter().getItem(i)
                                                 + "  ";

                                 }
                                 if (lv.getCheckedItemPositions().size() > 0)
                                 {
                                     new AlertDialog.Builder(Main.this)
                                             .setMessage(s).show();
                                 }
                                 else
                                 {
                                     new AlertDialog.Builder(Main.this)
                                             .setMessage("您未选择任何省份").show();

                                 }

                             }
                         }).setNegativeButton("取消", null).create();
         lv = ad.getListView();
         ad.show();

     }

     private class ButtonOnClick implements DialogInterface.OnClickListener
     {
         private int index;

         public ButtonOnClick(int index)
         {
             this.index = index;
         }

         @Override
         public void onClick(DialogInterface dialog, int whichButton)
         {
             if (whichButton >= 0)
             {
                 index = whichButton;
                 // dialog.cancel();
             }
             else
             {
                 if (whichButton == DialogInterface.BUTTON_POSITIVE)
                 {
                     new AlertDialog.Builder(Main.this).setMessage(
                             "您已经选择了： " + index + ":" + provinces[index]).show();
                 }
                 else if (whichButton == DialogInterface.BUTTON_NEGATIVE)
                 {
                     new AlertDialog.Builder(Main.this).setMessage("您什么都未选择.")
                             .show();

                 }
             }

         }

     }

     @Override
     public void onClick(View view)
     {
         switch (view.getId())
         {
             case R.id.btnListDialog:
             {
                 showListDialog();
                 break;
             }
             case R.id.btnSingleChoiceDialog:
             {
                 showSingleChoiceDialog();
                 break;
             }
             case R.id.btnMultiChoiceDialog:
             {
                 showMultiChoiceDialog();
                 break;
             }
         }
     }

     @Override
     public void onCreate(Bundle savedInstanceState)
     {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.main);
         Button btnListDialog = (Button) findViewById(R.id.btnListDialog);
         Button btnSingleChoiceDialog = (Button) findViewById(R.id.btnSingleChoiceDialog);
         Button btnMultiChoiceDialog = (Button) findViewById(R.id.btnMultiChoiceDialog);
         btnListDialog.setOnClickListener(this);
         btnSingleChoiceDialog.setOnClickListener(this);
         btnMultiChoiceDialog.setOnClickListener(this);
     }
 }