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

 
  1 package net.blogjava.mobile;
  2 
  3 import android.app.Activity;
  4 import android.app.AlertDialog;
  5 import android.content.DialogInterface;
  6 import android.os.Bundle;
  7 import android.view.View;
  8 import android.view.View.OnClickListener;
  9 import android.widget.Button;
 10 import android.widget.ListView;
 11 
 12 public class Main extends Activity implements OnClickListener
 13 {
 14     private String[] provinces = new String[]
 15     { "辽宁省", "山东省", "河北省", "福建省", "广东省", "黑龙江省" };
 16     private ButtonOnClick buttonOnClick = new ButtonOnClick(1);
 17     private ListView lv = null;
 18     private void showListDialog()
 19     {
 20         new AlertDialog.Builder(this).setTitle("选择省份").setItems(provinces,
 21                 new DialogInterface.OnClickListener()
 22                 {
 23                     public void onClick(DialogInterface dialog, int which)
 24                     {
 25                         final AlertDialog ad = new AlertDialog.Builder(
 26                                 Main.this).setMessage(
 27                                 "您已经选择了: " + which + ":" + provinces[which])
 28                                 .show();
 29                         android.os.Handler hander = new android.os.Handler();
 30                         hander.postDelayed(new Runnable()
 31                         {
 32                             @Override
 33                             public void run()
 34                             {
 35                                 ad.dismiss();
 36 
 37                             }
 38                         }, 5 * 1000);
 39 
 40                     }
 41                 }).show();
 42     }
 43 
 44     private void showSingleChoiceDialog()
 45     {
 46 
 47         new AlertDialog.Builder(this).setTitle("选择省份").setSingleChoiceItems(
 48                 provinces, 1, buttonOnClick).setPositiveButton("确定",
 49                 buttonOnClick).setNegativeButton("取消", buttonOnClick).show();
 50         
 51     }
 52 
 53 
 54     private void showMultiChoiceDialog()
 55     {
 56 
 57         AlertDialog ad = new AlertDialog.Builder(this)
 58                 .setIcon(R.drawable.image).setTitle("选择省份")
 59                 .setMultiChoiceItems(provinces, new boolean[]
 60                 { false, true, false, true, false, false },
 61                         new DialogInterface.OnMultiChoiceClickListener()
 62                         {
 63                             public void onClick(DialogInterface dialog,
 64                                     int whichButton, boolean isChecked)
 65                             {
 66 
 67                             }
 68                         }).setPositiveButton("确定",
 69                         new DialogInterface.OnClickListener()
 70                         {
 71                             public void onClick(DialogInterface dialog,
 72                                     int whichButton)
 73                             {
 74                                 int count = lv.getCount();
 75                                 String s = "您选择了:";
 76                                 for (int i = 0; i < provinces.length; i++)
 77                                 {
 78 
 79                                     if (lv.getCheckedItemPositions().get(i))
 80                                         s += i + ":"
 81                                                 + lv.getAdapter().getItem(i)
 82                                                 + "  ";
 83 
 84                                 }
 85                                 if (lv.getCheckedItemPositions().size() > 0)
 86                                 {
 87                                     new AlertDialog.Builder(Main.this)
 88                                             .setMessage(s).show();
 89                                 }
 90                                 else
 91                                 {
 92                                     new AlertDialog.Builder(Main.this)
 93                                             .setMessage("您未选择任何省份").show();
 94 
 95                                 }
 96 
 97                             }
 98                         }).setNegativeButton("取消", null).create();
 99         lv = ad.getListView();
100         ad.show();
101 
102     }
103 
104     private class ButtonOnClick implements DialogInterface.OnClickListener
105     {
106         private int index;
107 
108         public ButtonOnClick(int index)
109         {
110             this.index = index;
111         }
112 
113         @Override
114         public void onClick(DialogInterface dialog, int whichButton)
115         {
116             if (whichButton >= 0)
117             {
118                 index = whichButton;
119                 // dialog.cancel();                 
120             }
121             else
122             {
123                 if (whichButton == DialogInterface.BUTTON_POSITIVE)
124                 {
125                     new AlertDialog.Builder(Main.this).setMessage(
126                             "您已经选择了： " + index + ":" + provinces[index]).show();
127                 }
128                 else if (whichButton == DialogInterface.BUTTON_NEGATIVE)
129                 {
130                     new AlertDialog.Builder(Main.this).setMessage("您什么都未选择.")
131                             .show();
132 
133                 }
134             }
135 
136         }
137 
138     }
139 
140     @Override
141     public void onClick(View view)
142     {
143         switch (view.getId())
144         {
145             case R.id.btnListDialog:
146             {
147                 showListDialog();
148                 break;
149             }
150             case R.id.btnSingleChoiceDialog:
151             {
152                 showSingleChoiceDialog();
153                 break;
154             }
155             case R.id.btnMultiChoiceDialog:
156             {
157                 showMultiChoiceDialog();
158                 break;
159             }
160         }
161     }
162 
163     @Override
164     public void onCreate(Bundle savedInstanceState)
165     {
166         super.onCreate(savedInstanceState);
167         setContentView(R.layout.main);
168         Button btnListDialog = (Button) findViewById(R.id.btnListDialog);
169         Button btnSingleChoiceDialog = (Button) findViewById(R.id.btnSingleChoiceDialog);
170         Button btnMultiChoiceDialog = (Button) findViewById(R.id.btnMultiChoiceDialog);
171         btnListDialog.setOnClickListener(this);
172         btnSingleChoiceDialog.setOnClickListener(this);
173         btnMultiChoiceDialog.setOnClickListener(this);
174     }
175 }
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原文地址：https://www.cnblogs.com/hixin/p/4154688.html