Android開發學習筆記：Android很有用的代碼片段

1：查看是否有存儲卡插入
String status=Environment.getExternalStorageState();
if(status.equals(Enviroment.MEDIA_MOUNTED)){
   說明有SD卡插入
}

2：讓某個Activity透明
OnCreate 中不設Layout
this.setTheme(R.style.Theme_Transparent);
以下是 Theme_Transparent的定義（注意transparent_bg是一副透明的圖片）

3：在屏幕元素中設置句柄
使用Activity.findViewById來取得屏幕上的元素的句柄. 使用該句柄您可以設置或獲取任何該對象外露的值.
TextView msgTextView = (TextView)findViewById(R.id.msg);
   msgTextView.setText(R.string.push_me);

4:發送短信

            String body=”this is mms demo”;

           Intent mmsintent = new Intent(Intent.ACTION_SENDTO, Uri.fromParts(”smsto”, number, null));
           mmsintent.putExtra(Messaging.KEY_ACTION_SENDTO_MESSAGE_BODY, body);
           mmsintent.putExtra(Messaging.KEY_ACTION_SENDTO_COMPOSE_MODE, true);
           mmsintent.putExtra(Messaging.KEY_ACTION_SENDTO_EXIT_ON_SENT, true);
            startActivity(mmsintent);

   5:發送彩信

           StringBuilder sb = new StringBuilder();

            sb.append(”file://”);

            sb.append(fd.getAbsoluteFile());

            Intent intent = new Intent(Intent.ACTION_SENDTO, Uri.fromParts(”mmsto”, number, null));
            // Below extra datas are all optional.
            intent.putExtra(Messaging.KEY_ACTION_SENDTO_MESSAGE_SUBJECT, subject);
            intent.putExtra(Messaging.KEY_ACTION_SENDTO_MESSAGE_BODY, body);
            intent.putExtra(Messaging.KEY_ACTION_SENDTO_CONTENT_URI, sb.toString());
            intent.putExtra(Messaging.KEY_ACTION_SENDTO_COMPOSE_MODE, composeMode);
            intent.putExtra(Messaging.KEY_ACTION_SENDTO_EXIT_ON_SENT, exitOnSent);

            startActivity(intent);

7：發送Mail

             mime = “img/jpg”;
            shareIntent.setDataAndType(Uri.fromFile(fd), mime);
            shareIntent.putExtra(Intent.EXTRA_STREAM, Uri.fromFile(fd));
            shareIntent.putExtra(Intent.EXTRA_SUBJECT, subject);

            shareIntent.putExtra(Intent.EXTRA_TEXT, body);

8:註冊一個 BroadcastReceiver

registerReceiver(mMasterResetReciever, new IntentFilter(”oms.action.MASTERRESET”));

private BroadcastReceiver mMasterResetReciever = new BroadcastReceiver() {

        public void onReceive(Context context, Intent intent){
            String action = intent.getAction();
            if(”oms.action.MASTERRESET”.equals(action)){
                RecoverDefaultConfig();
            }
        }

    };

9:定義ContentObserver，監聽某個數據表

private ContentObserver mDownloadsObserver = new DownloadsChangeObserver(Downloads.CONTENT_URI);

private class DownloadsChangeObserver extends ContentObserver {
        public DownloadsChangeObserver(Uri uri) {
            super(new Handler());

        }

        @Override
        public void onChange(boolean selfChange) {｝
        }


10:獲得 手機UA

public String getUserAgent(){
    String user_agent = ProductProperties.get(ProductProperties.USER_AGENT_KEY, null);
            return user_agent;
    }

11：清空手機上Cookie

CookieSyncManager.createInstance(getApplicationContext());
        CookieManager.getInstance().removeAllCookie();

12：建立GPRS 連接

   //Dial the GPRS link.
    private boolean openDataConnection() {
        // Set up data connection.
        DataConnection conn = DataConnection.getInstance();

            if (connectMode == 0) {
                ret = conn.openConnection(mContext, “cmwap”, “cmwap”, “cmwap”);
            } else {
                ret = conn.openConnection(mContext, “cmnet”, “”, “”);
            }

    }

13：PreferenceActivity 用法

public class Setting extends PreferenceActivity｛
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.settings)；
    }

｝

Setting.xml:

            android:key=”seting2″
            android:title=”@string/seting2″
            android:summary=”@string/seting2″/>

            android:key=”seting1″
            android:title=”@string/seting1″
            android:summaryOff=”@string/seting1summaryOff”
            android:summaryOn=”@stringseting1summaryOff”/>

14:通過 HttpClient從指定server獲取數據

             DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpGet method = new HttpGet(“http://www.baidu.com/1.html”);
            HttpResponse resp;
            Reader reader = null;
            try {
                // AllClientPNames.TIMEOUT
                HttpParams params = new BasicHttpParams();
                params.setIntParameter(AllClientPNames.CONNECTION_TIMEOUT, 10000);
                httpClient.setParams(params);
                resp = httpClient.execute(method);
                int status = resp.getStatusLine().getStatusCode();

                if (status != HttpStatus.SC_OK) return false;

                // HttpStatus.SC_OK;
                return true;
            } catch (ClientProtocolException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } finally {
                if (reader != null) try {
                    reader.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }

15:顯示toast
Toast.makeText(this._getApplicationContext(), R.string._item, Toast.LENGTH_SHORT).show();

16:在當前Activity中啓動另外一個Activity
startActivity(new Intent(this,目標Activity.class));

17:從當前ContentView從查找控件
(Button)findViewById(R.id.btnAbout)
 R.id.btnAbout指控件id。

18:獲取屏幕寬高
DisplayMetrics dm = new DisplayMetrics();
//獲取窗口屬性
 getWindowManager().getDefaultDisplay().getMetrics(dm);
 int screenWidth = dm.widthPixels;//320
 int screenHeight = dm.heightPixels;//480

19:無標題欄、全屏
//無標題欄
requestWindowFeature(Window.FEATURE_NO_TITLE);
//全屏模式
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
  WindowManager.LayoutParams.FLAG_FULLSCREEN);
注意在setContentView()之前調用，否則無效。

20註冊activity
所有用到的Activity都必須在AndroidManifest.xml中註冊，否則會報空指針錯誤。
如：，注意是包名+類名。