ANDROID开发小技巧-1，android小技巧-1,1,如何截取当前屏幕(不

ANDROID开发小技巧-1，android小技巧-1,1,如何截取当前屏幕(不

打算记录一些自己在开发过程中遇到的一些技巧性代码，就从这篇开始吧。

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：
View rootView = getWindow().getDecorView().findViewById(android.R.id.content);
或者：
View rootView = findViewById(android.R.id.content);
或者：
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:
public static Bitmap getScreenShot(View view) {
    View screenView = view.getRootView();
    screenView.setDrawingCacheEnabled(true);
    Bitmap bitmap = Bitmap.createBitmap(screenView.getDrawingCache());
    screenView.setDrawingCacheEnabled(false);
    return bitmap;
}
c,将当前屏幕的截屏保存至SDCard:
private final static String dir = Environment.getExternalStorageDirectory().getAbsolutePath() + "/Screenshots";
public static void store(Bitmap bm, String fileName){
    File dir = new File(dir);
    if(!dir.exists())
      dir.mkdirs();
    File file = new File(dir, fileName);
    try {
        FileOutputStream fOut = new FileOutputStream(file);
        bm.compress(Bitmap.CompressFormat.PNG, 85, fOut);
        fOut.flush();
        fOut.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}
d,最后将该图片文件分享出来:
private void shareImage(String file){
    Uri uri = Uri.fromFile(file);
    Intent intent = new Intent();
    intent.setAction(Intent.ACTION_SEND);
    intent.setType("image/*");
    intent.putExtra(android.content.Intent.EXTRA_SUBJECT, "");
    intent.putExtra(android.content.Intent.EXTRA_TEXT, "");
    intent.putExtra(Intent.EXTRA_STREAM, uri);
    startActivity(Intent.createChooser(intent, "Share Screenshot"));
}

2,如何对HTML5中的视频截图:

a,初始化WebView:
String webUrl = ...; 
VideoView vv;
mWebView = (WebView) findViewById(R.id.webview);
mWebView.setWebChromeClient(chromeClient);
mWebView.setWebViewClient(wvClient);
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.getSettings().setPluginsEnabled(true);
mWebView.loadUrl(webUrl);
b,覆盖WebChromeClient中的onShowCustomView方法:
@Override
public void onShowCustomView(View view, CustomViewCallback callback) {
    super.onShowCustomView(view, callback);
    if (view instanceof FrameLayout){
        FrameLayout frame = (FrameLayout) view;
        if (frame.getFocusedChild() instanceof VideoView){
            vv = (VideoView) frame.getFocusedChild();
        }
    }
}
c,截取VideoView中播放的视频内容:
private Bitmap capture(VideoView vv){
    MediaMetadataRetriever rev = new MediaMetadataRetriever();
    rev.setDataSource(this, uri);//this is a Context; 
    Bitmap bitmap = rev.getFrameAtTime(vv.getCurrentPosition() * 1000, MediaMetadataRetriever.OPTION_CLOSEST_SYNC);
    return bitmap;
}
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:
\integer-array\ name="frag_home_ids"\
\item\@drawable/frag_home_credit_return_money\/item\
\item\@drawable/frag_home_transfer\/item\
\item\@drawable/frag_home_balance\/item\
\item\@drawable/frag_home_charge\/item\
\item\@drawable/frag_home_finance_cdd\/item\
\item\@drawable/frag_home_finance_ybjr\/item\
\item\@drawable/frag_home_more\/item\
\/integer-array\
b,通过编码的方式获取integer-array中的资源id整型值:
TypedArray tArray = getResources().obtainTypedArray(R.array.frag_home_ids);
int count = tArray.length();
int[] ids = new int[count];
for (int i = 0; i < ids.length; i++) {
    ids[i] = tArray.getResourceId(i, 0);
}
c,使用已经获取到的资源的id:
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:

private void refreshPartially(int position){
    int firstVisiblePosition = listview.getFirstVisiblePosition();
    int lastVisiblePosition = listview.getLastVisiblePosition();
    if(position>=firstVisiblePosition && position<=lastVisiblePosition){
        View view = listview.getChildAt(position - firstVisiblePosition);
        if(view.getTag() instanceof ViewHolder){
            ViewHolder vh = (ViewHolder)view.getTag();
           //holder.play.setBackgroundResource(resId);//Do something here.
            ...
        }
    }
}

5,Google Volley的单例模式实现:

package me.pc.mobile.tv.util;

import android.content.Context;
import android.graphics.Bitmap;
import android.util.LruCache;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.ImageLoader;
import com.android.volley.toolbox.Volley;

public class VolleySingleton {
private static VolleySingleton instance;
private RequestQueue requestQueue;
private ImageLoader imageLoader;
private VolleySingleton(Context context) {
requestQueue = Volley.newRequestQueue(context);
imageLoader = new ImageLoader(requestQueue, new ImageLoader.ImageCache() {
private final LruCache cache = new LruCache(20);

@Override
public Bitmap getBitmap(String url) {
    return cache.get(url);
}

@Override
public void putBitmap(String url, Bitmap bitmap) {
    cache.put(url, bitmap);
}
});
}

public static VolleySingleton getInstance(Context context) {
    if (instance == null) {
        instance = new VolleySingleton(context);
    }
    return instance;
}

public RequestQueue getRequestQueue() {
    return requestQueue;
}

public ImageLoader getImageLoader() {
    return imageLoader;
}
}

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:

public class PhotoMultipartRequest extends Request {

private static final String FILE_PART_NAME = "file";

private MultipartEntityBuilder mBuilder = MultipartEntityBuilder.create();
private final Response.Listener mListener;
private final File mImageFile;
protected Map headers;

public PhotoMultipartRequest(String url, ErrorListener errorListener, Listener listener, File imageFile){
    super(Method.POST, url, errorListener);

    mListener = listener;
    mImageFile = imageFile;

    buildMultipartEntity();
}

@Override
public Map getHeaders() throws AuthFailureError {
    Map headers = super.getHeaders();

    if (headers == null || headers.equals(Collections.emptyMap())) {
        headers = new HashMap();
    }

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

    return headers;
}

private void buildMultipartEntity(){
    mBuilder.addBinaryBody(FILE_PART_NAME, mImageFile, ContentType.create("image/jpeg"), mImageFile.getName());
    mBuilder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);
    mBuilder.setLaxMode().setBoundary("xx").setCharset(Charset.forName("UTF-8"));
}

@Override
public String getBodyContentType(){
    String contentTypeHeader = mBuilder.build().getContentType().getValue();
    return contentTypeHeader;
}

@Override
public byte[] getBody() throws AuthFailureError{
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    try {
        mBuilder.build().writeTo(bos);
    } catch (IOException e) {
        VolleyLog.e("IOException writing to ByteArrayOutputStream bos, building the multipart request.");
    }
    return bos.toByteArray();
}

@Override
protected Response parseNetworkResponse(NetworkResponse response) {
    T result = null;
    return Response.success(result, HttpHeaderParser.parseCacheHeaders(response));
}

@Override
protected void deliverResponse(T response) {
    mListener.onResponse(response);
}
}

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

原文