android 特殊用法琐碎二

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", "test@test.com", 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);

5scrollView 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();
}
}