来源: 互联网  发布时间: 2014-02-18

ProgressDialog 使用
ProgressDialog

[功能]
ProgressDialog 也是一种Dialog
一般 在出现ProgressDialog  后台都会再开辟Thread 来做一些耗时的工作 我演示的是从100数到0 这段时间既不太长 不用浪费时间等待 同时 也能明显地看出效果



[代码]
1. ProgressDialog 使用

public void startProgress(){
    	//to start Progress
    	pd = ProgressDialog.show(this, "loop from 100 to 0!", "is looping...", true,
    			false);
    	//pd.setIcon(R.drawable.icon);
    }

2. 开辟一个Thread来从100数到0 在数完后 关闭ProgressDialog

public class TaskLoop implements Runnable {
		@Override
		public void run() {
			// TODO Auto-generated method stub
			loop(5000);
			
			messageListener.sendEmptyMessage(TASK_LOOP_COMPLETE);
		}
    	
    }

public void loop(long i){
    	long j = i;
    	while(j>0){
    		Log.d("tag",j+"");
    		
    		j = j-1;
		}

    }

3. 运行该Thread

Thread loop = new Thread(new TaskLoop());
loop.start();

4.定义一个Handler 用于接受 关闭ProgressDialog 的通知

private Handler messageListener = new Handler(){
    	public void handleMessage(Message msg) {
			switch(msg.arg1){
			case TASK_LOOP_COMPLETE:
				pd.dismiss();
				break;
				
			}
		}
    };

[所有代码]

public class MyProgressUsage extends Activity {
	public final static int TASK_LOOP_COMPLETE = 0;
	
	ProgressDialog pd;
	
	TextView tv;
	/** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        findViewById(R.id.start).setOnClickListener(new OnClickListener(){
			public void onClick(View v) {
				// TODO Auto-generated method stub
				startLoop();
			}
        });
    }
    
    public void startLoop(){
    	
    	startProgress();
    	
    	Thread loop = new Thread(new TaskLoop());
    	loop.start();
    }
    
    
    public class TaskLoop implements Runnable {
		@Override
		public void run() {
			// TODO Auto-generated method stub
			loop(5000);
			
			messageListener.sendEmptyMessage(TASK_LOOP_COMPLETE);
		}
    	
    }
    
    public void startProgress(){
    	//to start Progress
    	pd = ProgressDialog.show(this, "loop from 100 to 0!", "is looping...", true,
    			false);
    	//pd.setIcon(R.drawable.icon);
    }
    
    //to do some time-cost task
    public void loop(long i){
    	long j = i;
    	while(j>0){
    		Log.d("tag",j+"");
    		
    		j = j-1;
		}

    }
    
    private Handler messageListener = new Handler(){
    	public void handleMessage(Message msg) {
			switch(msg.arg1){
			case TASK_LOOP_COMPLETE:
				pd.dismiss();
				break;
				
			}
		}
    };
    
}

http://dl.iteye.com/upload/picture/pic/52676/11cd6622-cb13-337a-bd52-007185e972c0.png
over!

    

    来源: 互联网  发布时间: 2014-02-18

GridView 网格布局 使用

GridView

 

[功能]

以前提及过GridView 说也是一种AdapterView 和ListView有点像 今天花了时间 用了一些 有点心得 和大家分享分享

 

 

[思路]

1. 既然和ListView像 那么应该还是通过 setAdapter() 来设置吧

2. 因为我想显示的是一些图片信息 必须用到ImageView 不是默认的Adapter用到的TextView 所以只能自己扩展了

 

 

[代码]

1. 定义包含GridView 的 main.xmk

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<GridView  
	android:id="@+id/gride"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:numColumns="3"
    android:verticalSpacing="5dip"
    />
</LinearLayout>

 

这行应该注意一下：

android:numColumns="3"

 

用来设定GridView每行显示的View数目 如果没有这行 会默认每行显示一个View 和ListView 的一样

 

 

2. 自定义 class ImageList extends BaseAdapter 其中主要是：

 

用于显示目标ImageView

 

public class ImageList extends BaseAdapter {
    	Activity activity;
    	
    	//construct
    	public ImageList(Activity a ) {
    		activity = a;
    	}
    	
		@Override
		public int getCount() {
			// TODO Auto-generated method stub
			return image.length;
		}

		@Override
		public Object getItem(int position) {
			// TODO Auto-generated method stub
			return image[position];
		}

		@Override
		public long getItemId(int position) {
			// TODO Auto-generated method stub
			return position;
		}

		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			// TODO Auto-generated method stub
			ImageView iv = new ImageView(activity);
			iv.setImageResource(image[position]);
			return iv;
		}
    }

 

 

3. 给GridView指定Adapter

GridView gv = (GridView) findViewById(R.id.gride);
        
        ImageList adapter = new ImageList(this);
        	
        gv.setAdapter(adapter);

 

 

 

所以最后效果图是这样的 网格布局

    

    来源: 互联网  发布时间: 2014-02-18

获得下载文件的长度

List values = urlConnection.getHeaderFields().get("content-Length") 
if (values != null && !values.isEmpty()) { 
 
    // getHeaderFields() returns a Map with key=(String) header  
    // name, value = List of String values for that header field.  
    // just use the first value here. 
    String sLength = (String) values.get(0); 
 
    if (sLength != null) { 
       //parse the length into an integer... 
       ... 
    } 

下面是可以参考的代码

Download.java

import java.io.*;
import java.net.*;
import java.util.*;

// This class downloads a file from a URL.
class Download extends Observable implements Runnable {
    
    // Max size of download buffer.
    private static final int MAX_BUFFER_SIZE = 1024;
    
    // These are the status names.
    public static final String STATUSES[] = {"Downloading",
    "Paused", "Complete", "Cancelled", "Error"};
    
    // These are the status codes.
    public static final int DOWNLOADING = 0;
    public static final int PAUSED = 1;
    public static final int COMPLETE = 2;
    public static final int CANCELLED = 3;
    public static final int ERROR = 4;
    
    private URL url; // download URL
    private int size; // size of download in bytes
    private int downloaded; // number of bytes downloaded
    private int status; // current status of download
    
    // Constructor for Download.
    public Download(URL url) {
        this.url = url;
        size = -1;
        downloaded = 0;
        status = DOWNLOADING;
        
        // Begin the download.
        download();
    }
    
    // Get this download's URL.
    public String getUrl() {
        return url.toString();
    }
    
    // Get this download's size.
    public int getSize() {
        return size;
    }
    
    // Get this download's progress.
    public float getProgress() {
        return ((float) downloaded / size) * 100;
    }
    
    // Get this download's status.
    public int getStatus() {
        return status;
    }
    
    // Pause this download.
    public void pause() {
        status = PAUSED;
        stateChanged();
    }
    
    // Resume this download.
    public void resume() {
        status = DOWNLOADING;
        stateChanged();
        download();
    }
    
    // Cancel this download.
    public void cancel() {
        status = CANCELLED;
        stateChanged();
    }
    
    // Mark this download as having an error.
    private void error() {
        status = ERROR;
        stateChanged();
    }
    
    // Start or resume downloading.
    private void download() {
        Thread thread = new Thread(this);
        thread.start();
    }
    
    // Get file name portion of URL.
    private String getFileName(URL url) {
        String fileName = url.getFile();
        return fileName.substring(fileName.lastIndexOf('/') + 1);
    }
    
    // Download file.
    public void run() {
        RandomAccessFile file = null;
        InputStream stream = null;
        
        try {
            // Open connection to URL.
            HttpURLConnection connection =
                    (HttpURLConnection) url.openConnection();
            
            // Specify what portion of file to download.
            connection.setRequestProperty("Range",
                    "bytes=" + downloaded + "-");
            
            // Connect to server.
            connection.connect();
            
            // Make sure response code is in the 200 range.
            if (connection.getResponseCode() / 100 != 2) {
                error();
            }
            
            // Check for valid content length.
            int contentLength = connection.getContentLength();
            if (contentLength < 1) {
                error();
            }
            
      /* Set the size for this download if it
         hasn't been already set. */
            if (size == -1) {
                size = contentLength;
                stateChanged();
            }
            
            // Open file and seek to the end of it.
            file = new RandomAccessFile(getFileName(url), "rw");
            file.seek(downloaded);
            
            stream = connection.getInputStream();
            while (status == DOWNLOADING) {
        /* Size buffer according to how much of the
           file is left to download. */
                byte buffer[];
                if (size - downloaded > MAX_BUFFER_SIZE) {
                    buffer = new byte[MAX_BUFFER_SIZE];
                } else {
                    buffer = new byte[size - downloaded];
                }
                
                // Read from server into buffer.
                int read = stream.read(buffer);
                if (read == -1)
                    break;
                
                // Write buffer to file.
                file.write(buffer, 0, read);
                downloaded += read;
                stateChanged();
            }
            
      /* Change status to complete if this point was
         reached because downloading has finished. */
            if (status == DOWNLOADING) {
                status = COMPLETE;
                stateChanged();
            }
        } catch (Exception e) {
            error();
        } finally {
            // Close file.
            if (file != null) {
                try {
                    file.close();
                } catch (Exception e) {}
            }
            
            // Close connection to server.
            if (stream != null) {
                try {
                    stream.close();
                } catch (Exception e) {}
            }
        }
    }
    
    // Notify observers that this download's status has changed.
    private void stateChanged() {
        setChanged();
        notifyObservers();
    }
}