android特殊用法

一些android特殊用法

1.让一个图片透明：

                   Bitmap buffer = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_4444);buffer.eraseColor(Color.TRANSPARENT);  

2.直接发送邮件：

                 Intent intent = new Intent(Intent.ACTION_SENDTO,  Uri .fromParts("mailto", "", null));    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);     context.startActivity(intent);   

3.程序控制屏幕变亮：

             WindowManager.LayoutParams lp = getWindow().getAttributes();     lp.screenBrightness = 100 / 100.0f;     getWindow().setAttributes(lp);  

4.过滤特定文本

                Filter filter = myAdapter.getFilter();     filter.filter(mySearchText);   

5.scrollView scroll停止事件

               setOnScrollListener(new OnScrollListener(){        public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {         // TODO Auto-generated method stub    }        public void onScrollStateChanged(AbsListView view, int scrollState) {          // TODO Auto-generated method stub          if(scrollState == 0) Log.i("a", "scrolling stopped...");    }  });}   

6. 对于特定的程序 发起一个关联供打开

               Bitmap bmp = getImageBitmap(jpg);     String path = getFilesDir().getAbsolutePath() + "/test.png";     File file = new File(path);     FileOutputStream fos = new FileOutputStream(file);     bmp.compress( CompressFormat.PNG, 100, fos );       fos.close();              Intent intent = new Intent();        intent.setAction(android .content.Intent.ACTION_VIEW);        intent.setDataAndType(Uri .fromFile(new File(path)), "image/png");        startActivity(intent);    

 
对于图片上边的不适用索引格式会出错。    

                  Intent intent = new Intent();      intent.setAction(android .content.Intent.ACTION_VIEW);      File file = new File("/sdcard/test.mp4");      intent.setDataAndType(Uri .fromFile(file), "video/*");      startActivity(intent);        Intent intent = new Intent();      intent.setAction(android .content.Intent.ACTION_VIEW);      File file = new File("/sdcard/test.mp3");      intent.setDataAndType(Uri .fromFile(file), "audio/*");      startActivity(intent);   

7.设置文本外观

                  setTextAppearance(context, android .R.style.TextAppearance_Medium);     android :textAppearance="?android :attr/textAppearanceMedium"  

8.设置单独的发起模式：

                <activity              android :name=".ArtistActivity"              android :label="Artist"              android :launchMode="singleTop">          </activity>        Intent i = new Intent();               i.putExtra(EXTRA_KEY_ARTIST, id);               i.setClass(this, ArtistActivity.class);                i.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);                startActivity(i);   

9.创建一个圆角图片
这个的主要原理其实就是利用遮罩，先创建一个圆角方框 然后将图片放在下面：

                Bitmap myCoolBitmap = ... ;          int w = myCoolBitmap.getWidth(), h = myCoolBitmap.getHeight();          Bitmap rounder = Bitmap.createBitmap(w,h,Bitmap.Config.ARGB_8888);          Canvas canvas = new Canvas(rounder);             Paint xferPaint = new Paint(Paint.ANTI_ALIAS_FLAG);          xferPaint.setColor(Color.RED);          canvas.drawRoundRect(new RectF(0,0,w,h), 20.0f, 20.0f, xferPaint);              xferPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));   //然后呢实现    canvas.drawBitmap(myCoolBitmap, 0,0, null);    canvas.drawBitmap(rounder, 0, 0, xferPaint);   

 

10.在notification 上的icon上加上数字 给人提示有多少个未读

                Notification notification = new Notification (icon, tickerText, when);    notification .number = 4;   

11背景渐变：
首先建立文件drawable/shape.xml

                 <?xml version="1.0" encoding="utf-8"?>    <shape xmlns:android ="http://schemas.android .com/apk/res/android " android :shape="rectangle">       <gradient android :startColor="#FFFFFFFF" android :endColor="#FFFF0000"                android :angle="270"/>    </shape>    

在该文件中设置渐变的开始颜色(startColor)、结束颜色(endColor)和角度(angle)

接着创建一个主题values/style.xml

                 <?xml version="1.0" encoding="utf-8"?>    <resources>    <style name="NewTheme" parent="android :Theme">    <item name="android :background">@drawable/shape</item>    </style>    </resources>   

然后在AndroidManifest.xml文件中的application或activity中引入该主题,如: 

      

              <activity android :name=".ShapeDemo" android :theme="@style/NewTheme">    

 

   该方法同样适用于控件  http://17f8.cn/trackback.php?tbID=259&extra=9d45e9

12. 储存数据 当你在一个实例中保存静态数据，此示例关闭后 下一个实例想引用 静态数据就会为null，这里呢必须重写applition

 

          public class MyApplication extends Application{          private String thing = null;          public String getThing(){                return thing;            }            public void setThing( String thing ){                this.thing = thing;    }          }          public class MyActivity extends Activity {             private MyApplication app;             public void onCreate(Bundle savedInstanceState) {                 super.onCreate(savedInstanceState);                 app = ((MyApplication)getApplication());                 String thing = app.getThing();             }          }