网上找了找，貌似要实现多维的动态数组还有多种方法，这里以Vector为例：
import java.util.Vector;
public class main {
public static void main(String[] args){
// TODO Auto-generated method stub
Vector vecFields = new Vector();
String[] ar1=new String[]{"a","b"};
String[] ar2=new String[]{"c","d","e"};
//定义两个字符串数组
vecFields.add(ar1);
vecFields.add(ar2);
//加入到vector
for(int i=0;i
Vector支持Object类型，我这里指定为String,也就是说任何类型，像int,float,boolean都是可以的
今天学习到Service，在用Service下载文件时，一个问题就是Service没有界面，如何通知用户当前下载的进度，Service直接向Activity传数据有点麻烦，于是想到了用Broadcast，Service广播，Activity负责接收，再对接收到的数据进行处理，就达到了我们的目的。下面是今天这个程序的运行效果： 
先注册Receiver,然后开始Service,上面的TextView和ProgressBar就会随着Service传过来的值变，解除注册Receiver或者结束Service后不会再变。 Service代码：
package com.services;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;
public class TestService extends Service {
boolean isStop=false;
@Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
Log.i("TAG","绑定");
return null;
}
public void onCreate(){
Log.i("TAG","Services onCreate");
super.onCreate();
}
public void onStart(Intent intent,int startId){
Log.i("TAG","Services onStart");
super.onStart(intent, startId);
new Thread(){//新建线程，每隔1秒发送一次广播，同时把i放进intent传出
public void run(){
int i=0;
while(!isStop){
Intent intent=new Intent();
intent.putExtra("i", i);
i++;
intent.setAction("android.intent.action.test");//action与接收器相同
sendBroadcast(intent);
Log.i("TAG",String.valueOf(i));
try {
sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}.start();
}
@Override
public void onDestroy() {
Log.i("TAG","Services onDestory");
isStop=true;//即使service销毁线程也不会停止，所以这里通过设置isStop来停止线程
super.onDestroy();
}
}
Activity代码:
package com.services;
import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
public class main extends Activity {
/** Called when the activity is first created. */
Button b1,b2,b3,b4;
TestService mService;
ProgressBar pb;
MyReceiver receiver;
TextView tv;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
b1=(Button)findViewById(R.id.b1);
b2=(Button)findViewById(R.id.b2);
b3=(Button)findViewById(R.id.b3);
b4=(Button)findViewById(R.id.b4);
b1.setOnClickListener(l1);
b2.setOnClickListener(l2);
b3.setOnClickListener(l3);
b4.setOnClickListener(l4);
pb=(ProgressBar)findViewById(R.id.pb);
tv=(TextView)findViewById(R.id.tv);
}
public class MyReceiver extends BroadcastReceiver {
//自定义一个广播接收器
@Override
public void onReceive(Context context, Intent intent) {
// TODO Auto-generated method stub
System.out.println("OnReceiver");
Bundle bundle=intent.getExtras();
int a=bundle.getInt("i");
pb.setProgress(a);
tv.setText(String.valueOf(a));
//处理接收到的内容
}
public MyReceiver(){
System.out.println("MyReceiver");
//构造函数，做一些初始化工作，本例中无任何作用
}
}
OnClickListener l1=new OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
startService(new Intent(main.this, TestService.class));
//开始服务
}
};
OnClickListener l2=new OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
stopService(new Intent(main.this, TestService.class));
//结束服务
}
};
OnClickListener l3=new OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
//注册接收器
receiver=new MyReceiver();
IntentFilter filter=new IntentFilter();
filter.addAction("android.intent.action.test");
main.this.registerReceiver(receiver,filter);
}
};
OnClickListener l4=new OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
main.this.unregisterReceiver(receiver);
//解除注册接收器
}
};
}
先说思路，首先让一张放在res/drawable里的图片代替网络图片，加进ListItem，现在显示的就是本地图片，然后新开一个线程循环下载网络图片，每下完一张，替换原来显示的本地图片，更新ListView。 刚开始做的时候，乱配器用的是SimpleAdapter，但是后来发现，SimpleAdapter只能加载放事先放在res/drawable，不能加载Bitmap,或者是Drawable,于是自己写了个适配器来继承SimpleAdapter,加入Bitmap支持，完美实现以上功能。
final ListView list = (ListView) findViewById(R.id.favlv);
list.setDivider(null);
list.setOnItemClickListener(Click);
myAdapter listItemAdapter;
ArrayList> listItem = new ArrayList>();
cursor=db.query("fav",new String[]{"id","title","url","thumb"},null,null,null,null,"id DESC");
UrlArr.clear();
ThumbArr.clear();
ItemID.clear();
if(cursor.getCount()>0){
nofav.setVisibility(View.INVISIBLE);
}
while(cursor.moveToNext()){
HashMap map = new HashMap();
map.put("ItemImage",R.drawable.load);//图像资源的ID
map.put("ItemTv",cursor.getString(1));
listItem.add(map);
UrlArr.add(cursor.getString(2));
ThumbArr.add(cursor.getString(3));
ItemID.add(cursor.getString(0));
}
cursor.close();
//以上内容是读取数据库，并把数据加到listItem上，没有数据库的自己看着改，ThumbArr存放的是图片URL，另两个是我项目里用的
listItemAdapter = new myAdapter(this,listItem,R.layout.favlv,new String[] {"ItemImage","ItemTv"},new int[] {R.id.ItemImage,R.id.ItemTv});
list.setAdapter(listItemAdapter);
list.setOnCreateContextMenuListener(MenuLis);
//新开线程循环下载图片
new Thread(){
@SuppressWarnings("unchecked")
public void run(){
int i=0;
while(i map = (HashMap)listItemAdapter.getItem(i);
map.put("ItemImage",bmp);
handler.sendEmptyMessage(0);//这个是更新通知就是listItemAdapter.notifyDataSetChanged();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
i++;
}
}
}.start();
下面的是myAdapter适配器代码：
package com.BottomMenu;
import java.util.List;
import java.util.Map;
import android.content.Context;
import android.graphics.Bitmap;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Checkable;
import android.widget.ImageView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
public class myAdapter extends SimpleAdapter {
private int[] mTo;
private String[] mFrom;
private ViewBinder mViewBinder;
private List> mData;
private int mResource;
private int mDropDownResource;
private LayoutInflater mInflater;
public myAdapter(Context context,
List> data, int resource, String[] from,
int[] to) {
super(context, data, resource, from, to);
mData = data;
mResource = mDropDownResource = resource;
mFrom = from;
mTo = to;
mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
/**
* @see android.widget.Adapter#getView(int, View, ViewGroup)
*/
public View getView(int position, View convertView, ViewGroup parent) {
return createViewFromResource(position, convertView, parent, mResource);
}
private View createViewFromResource(int position, View convertView,
ViewGroup parent, int resource) {
View v;
if (convertView == null) {
v = mInflater.inflate(resource, parent, false);
final int[] to = mTo;
final int count = to.length;
final View[] holder = new View[count];
for (int i = 0; i < count; i++) {
holder[i] = v.findViewById(to[i]);
}
v.setTag(holder);
} else {
v = convertView;
}
bindView(position, v);
return v;
}
private void bindView(int position, View view) {
final Map dataSet = mData.get(position);
if (dataSet == null) {
return;
}
final ViewBinder binder = mViewBinder;
final View[] holder = (View[]) view.getTag();
final String[] from = mFrom;
final int[] to = mTo;
final int count = to.length;
for (int i = 0; i < count; i++) {
final View v = holder[i];
if (v != null) {
final Object data = dataSet.get(from[i]);
// if(data i)
String text = data == null ? "" : data.toString();
if (text == null) {
text = "";
}
boolean bound = false;
if (binder != null) {
bound = binder.setViewValue(v, data, text);
}
if (!bound) {
if (v instanceof Checkable) {
if (data instanceof Boolean) {
((Checkable) v).setChecked((Boolean) data);
} else {
throw new IllegalStateException(v.getClass().getName() +
" should be bound to a Boolean, not a " + data.getClass());
}
} else if (v instanceof TextView) {
// Note: keep the instanceof TextView check at the bottom of these
// ifs since a lot of views are TextViews (e.g. CheckBoxes).
setViewText((TextView) v, text);
} else if (v instanceof ImageView) {
if (data instanceof Integer) {
setViewImage((ImageView) v, (Integer) data);
} else if(data instanceof Bitmap) {
setViewImage((ImageView) v, (Bitmap)data);
}
} else {
throw new IllegalStateException(v.getClass().getName() + " is not a " +
" view that can be bounds by this SimpleAdapter");
}
}
}
}
}
public void setViewImage(ImageView v, int value) {
v.setImageResource(value);
}
public void setViewImage(ImageView v, Bitmap bm) {
((ImageView) v).setImageBitmap(bm);
}
};
今天学习数据库操作。 先写个类继承SQLiteOpenHelper类：
package com.db;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
public class DBHelper extends SQLiteOpenHelper {
public static final int VERSION=1;
public DBHelper(Context context, String name, CursorFactory factory,
int version) {
super(context, name, factory, version);
// TODO Auto-generated constructor stub
}
public DBHelper(Context context, String name, int version) {
this(context, name, null, version);
// TODO Auto-generated constructor stub
}
public DBHelper(Context context, String name) {
this(context,name,VERSION);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
System.out.println("创建数据库");
db.execSQL("create table fav (id integer primary key autoincrement,title text not null,url text not null,thumb text not null);");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
System.out.println("升级数据库");
}
}
下面是在程序中增，改，删，查的方法
package com.db;
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.widget.TextView;
public class main extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
TextView tv=(TextView)findViewById(R.id.tv);
DBHelper dbHelper=new DBHelper(this,"youku");//youku为数据库名
//执行onCreate(),如果参数加版本号则执行onUpgrade()
SQLiteDatabase db=dbHelper.getWritableDatabase();
//getReadableDatabase或getWriteableDatabase后才创建数据库
//插入
ContentValues cv=new ContentValues();
cv.put("title","标题");
cv.put("url","http://url");
cv.put("thumb","http://thumb");
db.insert("fav", null, cv);
//insert into fav('title','url','thumb') values('标题','http://url','http://thumb');
//更新
cv.clear();
cv.put("title", "English");
db.update("fav",cv,"id=?",new String[]{"1"});
//update fav set title='english' where id='1'
//表名、ContentValues对象、where子句的条件加占位符，一个占位符对应后面的数组的一个元素,相当于id=1
//查询 select id,title,url,thumb from fav
Cursor cursor=db.query("fav",new String[]{"id","title","url","thumb"},null,null,null,null,null);
String s="";
while(cursor.moveToNext()){
s+=cursor.getString(0)+":"+cursor.getString(1)+"\n";
}
tv.setText(s);
//删除
db.delete("fav","id=?",new String[]{"3"});
//相当 于 delete from fav where id='3';
}
}
Bitmap转Drawble
Resources res=getResources();
Bitmap bm=BitmapFactory.decodeResource(res, R.drawable.header);
BitmapDrawable bitmapDrawable = new BitmapDrawable(bm);
Drawable drawable = (Drawable)bitmapDrawable;
Drawable 转Bitmap:
Bitmap bitmap = ((BitmapDrawable)drawable).getBitmap();
解决ListView拖动Item背景变黑问题， 在XML中的ListView标签中加上android:cacheColorHint属性，值设为需要的颜色即可,也可直接设为@null,即无色透明
默认情况下，如果视频分辨率小于屏幕分辨率，VideoView在播放视频时都是在左上角的，影响程序美观。 用下面的方法完美解决，视频居中播放
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
>
<VideoView
android:id="@+id/VideoView01"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
/>
</LinearLayout>
关键在父元素的layout_gravity,默认不设置是left
关闭所有Activity完全退出程序，网络上的方法基本都试过,但在android 2.2下只有这个有效果。
Intent startMain = new Intent(Intent.ACTION_MAIN);
startMain.addCategory(Intent.CATEGORY_HOME);
startMain.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(startMain);
System.exit(0);
执行后在任务管理器看不到
有时候，我们需要启动系统中安装的其他软件来做接下去的处理，可以用下面的方法做跳转：
Intent intent=new Intent();
intent.setClass("包名","包名.Activity名");
channel.this.startActivity(intent);
如果系统中不存在该包，或Activity，会FC。查看正在运行的程序包名，Activity名可以在连接手机的情况下，点击Eclipse右上角的Hierarchy View,就是在DDMS那，默认没显示，自己添加。
如果直接用下面的方法启动OnStop状态的Activity
Intent intent=new Intent();
intent.setClass(channel.this, main.class);
channel.this.startActivity(intent);
相当于重新启动一个新的Activity,会重新执行OnCreate方法，导致系统资源的浪费。可以在Intent里加上下面一句来解决：
intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
这样，启动的Activity就不会再执行OnCreate方法，直接就OnRestart.