Android开发Tips-1

打算记录一些自己在开发过程中遇到的一些技巧性代码，方便以后遇到相似功能时能够快速的找到，那就从这里开始吧。

 

1,如何截取当前屏幕(不包括当前Activity的Title)并分享：

a,获取当前Activity的根视图：
 1 View rootView = getWindow().getDecorView().findViewById(android.R.id.content); 
或者：
 1 View rootView = findViewById(android.R.id.content); 
或者：
 1 View rootView = findViewById(android.R.id.content).getRootView(); 
关于android.R.id.content，开发者文档中并没有给予说明，但经过测试它应该是用来获取setContentView()中设置的View。
b,截取当前根视图的屏幕:

1 public static Bitmap getScreenShot(View view) {

2     View screenView = view.getRootView();

3     screenView.setDrawingCacheEnabled(true);

4     Bitmap bitmap = Bitmap.createBitmap(screenView.getDrawingCache());

5     screenView.setDrawingCacheEnabled(false);

6     return bitmap;

7 }

getScreenShot

c,将当前屏幕的截屏保存至SDCard:

 1 private final static String dir = Environment.getExternalStorageDirectory().getAbsolutePath() + "/Screenshots";

 2 public static void store(Bitmap bm, String fileName){

 3     File dir = new File(dir);

 4     if(!dir.exists())

 5         dir.mkdirs();

 6     File file = new File(dir, fileName);

 7     try {

 8         FileOutputStream fOut = new FileOutputStream(file);

 9         bm.compress(Bitmap.CompressFormat.PNG, 85, fOut);

10         fOut.flush();

11         fOut.close();

12     } catch (Exception e) {

13         e.printStackTrace();

14     }

15 }

store(Bitmap bm, String fileName)

d,最后将该图片文件分享出来:

 1 private void shareImage(String file){

 2     Uri uri = Uri.fromFile(file);

 3     Intent intent = new Intent();

 4     intent.setAction(Intent.ACTION_SEND);

 5     intent.setType("image/*");

 6     intent.putExtra(android.content.Intent.EXTRA_SUBJECT, "");

 7     intent.putExtra(android.content.Intent.EXTRA_TEXT, "");

 8     intent.putExtra(Intent.EXTRA_STREAM, uri);

 9     startActivity(Intent.createChooser(intent, "Share Screenshot"));

10 }

shareImage(String file)

 

 

2,如何对HTML5中的视频截图:

a,初始化WebView:

1 String webUrl = ...; 

2 VideoView vv;

3 mWebView = (WebView) findViewById(R.id.webview);

4 mWebView.setWebChromeClient(chromeClient);

5 mWebView.setWebViewClient(wvClient);

6 mWebView.getSettings().setJavaScriptEnabled(true);

7 mWebView.getSettings().setPluginsEnabled(true);

8 mWebView.loadUrl(webUrl);

View Code

b,覆盖WebChromeClient中的onShowCustomView方法:

 1 @Override

 2 public void onShowCustomView(View view, CustomViewCallback callback) {

 3     super.onShowCustomView(view, callback);

 4     if (view instanceof FrameLayout){

 5         FrameLayout frame = (FrameLayout) view;

 6         if (frame.getFocusedChild() instanceof VideoView){

 7             vv = (VideoView) frame.getFocusedChild();

 8         }

 9     }

10 }

onShowCustomView(View view, CustomViewCallback callback)

c,截取VideoView中播放的视频内容:

1 private Bitmap capture(VideoView vv){

2     MediaMetadataRetriever rev = new MediaMetadataRetriever();

3     rev.setDataSource(this, uri);//this is a Context; 

4     Bitmap bitmap = rev.getFrameAtTime(vv.getCurrentPosition() * 1000, MediaMetadataRetriever.OPTION_CLOSEST_SYNC);

5     return bitmap;

6 }

capture(VideoView vv)

d,如何还想将截屏幕保存或分享，请参见上面的代码示例.

 

3,如何动态获取保存在integer-array中的动态资源id？

a,在res/values/目录下创建arrays.xml文件，创建内容如下:

1 <integer-array name="frag_home_ids">

2     <item>@drawable/frag_home_credit_return_money</item>

3     <item>@drawable/frag_home_transfer</item>

4     <item>@drawable/frag_home_balance</item>

5     <item>@drawable/frag_home_charge</item>

6     <item>@drawable/frag_home_finance_cdd</item>

7     <item>@drawable/frag_home_finance_ybjr</item>

8     <item>@drawable/frag_home_more</item>

9 </integer-array>

arrays.xml

b,通过编码的方式获取integer-array中的资源id整型值:

1 TypedArray tArray = getResources().obtainTypedArray(R.array.frag_home_ids);

2 int count = tArray.length();

3 int[] ids = new int[count];

4 for (int i = 0; i < ids.length; i++) {

5     ids[i] = tArray.getResourceId(i, 0);

6 }

View Code

c,使用已经获取到的资源的id:
 1 holder.iv.setImageResource(ids[position]); 
d,我们也还可以用这种方式获取string, color, integer, layout, menu等的id.

 

4,ListView或GridView局部刷新原理的实现:

 1 private void refreshPartially(int position){

 2     int firstVisiblePosition = listview.getFirstVisiblePosition();

 3     int lastVisiblePosition = listview.getLastVisiblePosition();

 4     if(position>=firstVisiblePosition && position<=lastVisiblePosition){

 5         View view = listview.getChildAt(position - firstVisiblePosition);

 6         if(view.getTag() instanceof ViewHolder){

 7             ViewHolder vh = (ViewHolder)view.getTag();

 8             //holder.play.setBackgroundResource(resId);//Do something here.

 9             ...

10         }

11     }

12 }

refreshPartially(int position)

 

5,Google Volley的单例模式实现:

 1 package me.pc.mobile.tv.util;

 2 

 3 import android.content.Context;

 4 import android.graphics.Bitmap;

 5 import android.util.LruCache;

 6 import com.android.volley.RequestQueue;

 7 import com.android.volley.toolbox.ImageLoader;

 8 import com.android.volley.toolbox.Volley;

 9 

10 public class VolleySingleton {    

11     private static VolleySingleton instance;

12     private RequestQueue requestQueue;

13     private ImageLoader imageLoader;

14     private VolleySingleton(Context context) {

15         requestQueue = Volley.newRequestQueue(context);

16         imageLoader = new ImageLoader(requestQueue, new ImageLoader.ImageCache() {

17             private final LruCache<string, bitmap=""> cache = new LruCache<string, bitmap="">(20);

18 

19             @Override

20             public Bitmap getBitmap(String url) {

21                 return cache.get(url);

22             }

23 

24             @Override

25             public void putBitmap(String url, Bitmap bitmap) {

26                 cache.put(url, bitmap);

27             }

28         });

29         }

30 

31     public static VolleySingleton getInstance(Context context) {

32         if (instance == null) {

33             instance = new VolleySingleton(context);

34         }

35         return instance;

36     }

37 

38     public RequestQueue getRequestQueue() {

39         return requestQueue;

40     }

41 

42     public ImageLoader getImageLoader() {

43         return imageLoader;

44     }

45 }

VolleySingleton.java

采用Volley的单例模式，就避免了在每一个Activity或Frament中都创建一个RequestQueue的麻烦.

 

6,使用Google Volley来实现文件的分块上传:

 1 public class PhotoMultipartRequest extends Request {

 2 

 3     private static final String FILE_PART_NAME = "file";

 4 

 5     private MultipartEntityBuilder mBuilder = MultipartEntityBuilder.create();

 6     private final Response.Listener mListener;

 7     private final File mImageFile;

 8     protected Map<string, string=""> headers;

 9 

10     public PhotoMultipartRequest(String url, ErrorListener errorListener, Listener listener, File imageFile){

11         super(Method.POST, url, errorListener);

12 

13         mListener = listener;

14         mImageFile = imageFile;

15 

16         buildMultipartEntity();

17     }

18 

19     @Override

20     public Map<string, string=""> getHeaders() throws AuthFailureError {

21         Map<string, string=""> headers = super.getHeaders();

22 

23         if (headers == null || headers.equals(Collections.emptyMap())) {

24             headers = new HashMap<string, string="">();

25         }

26 

27         headers.put("Accept", "application/json");

28 

29         return headers;

30     }

31 

32     private void buildMultipartEntity(){

33         mBuilder.addBinaryBody(FILE_PART_NAME, mImageFile, ContentType.create("image/jpeg"), mImageFile.getName());

34         mBuilder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);

35          mBuilder.setLaxMode().setBoundary("xx").setCharset(Charset.forName("UTF-8"));

36     }

37 

38     @Override

39     public String getBodyContentType(){

40         String contentTypeHeader = mBuilder.build().getContentType().getValue();

41         return contentTypeHeader;

42     }

43 

44     @Override

45     public byte[] getBody() throws AuthFailureError{

46         ByteArrayOutputStream bos = new ByteArrayOutputStream();

47         try {

48             mBuilder.build().writeTo(bos);

49         } catch (IOException e) {

50             VolleyLog.e("IOException writing to ByteArrayOutputStream bos, building the multipart request.");

51         }

52 

53         return bos.toByteArray();

54     }

55 

56     @Override

57     protected Response parseNetworkResponse(NetworkResponse response) {

58         T result = null;

59         return Response.success(result, HttpHeaderParser.parseCacheHeaders(response));

60     }

61 

62     @Override

63     protected void deliverResponse(T response) {

64         mListener.onResponse(response);

65     }

66 }            

PhotoMultipartRequest.java

代码中使用了Apache的httpclient.jar文件，用于实现文件的拆分与上传.

 

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