Android部分实用代码整理

android

读取字符串

private String readIt(InputStream stream, int len) throws IOException, UnsupportedEncodingException {
        Reader reader = null;
        reader = new InputStreamReader(stream, "UTF-8");
        char[] buffer = new char[len];
        reader.read(buffer);
        return new String(buffer);
    }

网络下载

private InputStream downloadUrl(String urlString) throws IOException {
        // BEGIN_INCLUDE(get_inputstream)
        URL url = new URL(urlString);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setReadTimeout(10000 /* milliseconds */);
        conn.setConnectTimeout(15000 /* milliseconds */);
        conn.setRequestMethod("GET");
        conn.setDoInput(true);
        // Start the query
        conn.connect();
        InputStream stream = conn.getInputStream();
        return stream;
        // END_INCLUDE(get_inputstream)
    }

图片下载

private void downloadImageFromUri(String address) {
    URL url;
    try {
        url = new URL(address);
    } catch (MalformedURLException e1) {
        url = null;
    }
    URLConnection conn;
    InputStream in;
    Bitmap bitmap;
    try {
        conn = url.openConnection();
        conn.connect();
        in = conn.getInputStream();
        bitmap = BitmapFactory.decodeStream(in); 
        in.close();
    } catch (IOException e) {
        bitmap = null;
    }
    if (bitmap != null) {
        ImageView img = (ImageView) findViewById(R.id.ivBasicImage); 
        img.setImageBitmap(bitmap); 
    } 
}

读取联系人

private void loadContacts() {
        Uri allContacts = Uri.parse("content://contacts/people");
        CursorLoader cursorLoader = new CursorLoader(this, allContacts, 
           null, // the columns to retrive 
           null, // the selection criteria
           null, // the selection args
           null // the sort order
        );
        Cursor c = cursorLoader.loadInBackground();
        if (c.moveToFirst()) { 
            do {
                 // Get Contact ID
                int idIndex = c.getColumnIndex(ContactsContract.Contacts._ID);
                String contactID = c.getString(idIndex);
                // Get Contact Name
                int nameIndex = c.getColumnIndex(ContactsContract.Contacts.DISPLAY_NAME);
                String contactDisplayName = c.getString(nameIndex);
                names.add(contactDisplayName);
                Log.d("debug", contactID + ", " + contactDisplayName); 
            } while (c.moveToNext());
        }
    }

获取TextView显示的字符串宽度

        TextView textView = (TextView) findViewById(R.id.test);
        textView.setText(text);
        int spec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
        textView.measure(spec, spec);
        // getMeasuredWidth
        int measuredWidth = textView.getMeasuredWidth();
        // new textpaint measureText
        TextPaint newPaint = new TextPaint();
        float textSize = getResources().getDisplayMetrics().scaledDensity * 15;
        newPaint.setTextSize(textSize);
        float newPaintWidth = newPaint.measureText(text);
        // textView getPaint measureText
        TextPaint textPaint = textView.getPaint();
        float textPaintWidth = textPaint.measureText(text);

Service中显示Status Bar Notifications

Notification notification = new Notification(R.drawable.icon, getText(R.string.ticker_text),
        System.currentTimeMillis());
Intent notificationIntent = new Intent(this, ExampleActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0);
notification.setLatestEventInfo(this, getText(R.string.notification_title),
        getText(R.string.notification_message), pendingIntent);
startForeground(ONGOING_NOTIFICATION_ID, notification);

结合AsyncTask与ProgressBar

private class TaskSeven extends AsyncTask<Void, Integer, Void> {
        int mValue = 0;
        @Override
        protected void onProgressUpdate(Integer... values) {
            super.onProgressUpdate(values);
            mTaskSevenPb.setProgress(mValue); //关键
        }
        @Override
        protected Void doInBackground(Void... params) {
            while (mValue < 100) {
                mValue += 20;
                publishProgress(mValue); //关键
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            return null;
        }
        @Override
        protected void onPostExecute(Void aVoid) {
            mSevenTv.setText("Over");
            Toast.makeText(getApplicationContext(),"TaskFour Ok",Toast.LENGTH_SHORT).show();
        }
    }

运用SharePreference存储和读区（注意权限）

    private static SharedPreferences mMusicSP;
    public static final String MUSIC_SP_KEY = "musicUrl";
    public static final String MUSIC_SP_DEFAULT = "noUrl";
    public static boolean saveMusicUrlByPf(Context context,String url) {
        mMusicSP = context.getSharedPreferences(context.getResources().getString(R.string.share_preferences_key)
                ,Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = mMusicSP.edit();
        editor.putString(MUSIC_SP_KEY,url);
        editor.commit();
        return true;
    }
    public static String getMusicUrlByPf(Context context) {
        mMusicSP = context.getSharedPreferences(context.getResources().getString(R.string.share_preferences_key)
                ,Context.MODE_PRIVATE);
        String tempUrl = mMusicSP.getString(MUSIC_SP_KEY,MUSIC_SP_DEFAULT);
        return tempUrl;
    }

按2次返回键退出程序

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(keyCode == KeyEvent.KEYCODE_BACK) {
            if ((System.currentTimeMillis() - mBackKeyTime) > 2000) {
                mBackKeyTime = System.currentTimeMillis();
                Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show();
            } else {
                finish();
            }
        }
        return true;
    }

显示／隐藏软件盘

InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);  
imm.showSoftInput(view,InputMethodManager.SHOW_FORCED);  //显示
imm.hideSoftInputFromWindow(view.getWindowToken(), 0);  //强制隐藏键盘

使背景模糊，用于启动的Tips

        getWindow().setFlags(WindowManager.LayoutParams.FLAG_BLUR_BEHIND,
                WindowManager.LayoutParams.FLAG_BLUR_BEHIND);

TextView使用技巧

• 设置图片：drawableTop(上),drawableButtom(下),drawableLeft(左),drawableRight(右)另外,你也可以使用drawablePadding来设置图片与文字间的间距！
• 使用autoLink属性识别链接类型

    TextView t1 = (TextView)findViewById(R.id.txtOne);
    String s1 = "<font color='blue'><b>百度一下，你就知道~：</b></font><br>";
    s1 += "<a href = 'http://www.baidu.com'>百度</a>";
    t1.setText(Html.fromHtml(s1));
    t1.setMovementMethod(LinkMovementMethod.getInstance());

• 可为图片添加超链接

巧用String分割

    public final static String[] DEFAULT_SECTIONS = "常用 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z".split(" ");

验证邮箱

    private boolean validEmail(String email){
        Pattern emailPattern=Pattern.compile("\\w+([-+.]\\w+)*@\\w+([-.]\\w+)*\\.\\w+([-.]\\w+)*");
        Matcher emailMatcher=emailPattern.matcher(email);
        return emailMatcher.matches();
    }

调用系统接口发送短信

        Uri smsToUri = Uri.parse( "smsto:" ); // This ensures only SMS apps respond
        Intent intent = new Intent(Intent.ACTION_SENDTO , smsToUri);
        intent.putExtra("sms_body", message);
        intent.putExtra("address", phoneNumber);
        if (intent.resolveActivity(getPackageManager()) != null) {
            startActivity(intent);
        }

Activity的切换动画

 overridePendingTransition(SLIDE_UP_IN, SLIDE_DOWN_OUT);

Activity的切换动画指的是从一个activity跳转到另外一个activity时的动画。用2个xml来传递参数，anim下

设置FLAG_ACTIVITY_CLEAR_TOP来清除历史栈

    Intent intent = new Intent(mContext, MainActivity.class);
    intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
    startActivity(intent);

提醒是否关闭开发者不保留活动

int alwaysFinish = Settings.Global.getInt(getContentResolver(), Settings.Global.ALWAYS_FINISH_ACTIVITIES, 0);  
if (alwaysFinish == 1) {  
            Dialog dialog = null;  
            dialog = new AlertDialog.Builder(this)  
                    .setMessage(  
                            "由于您已开启'不保留活动',导致部分功能无法正常使用.我们建议您点击左下方'设置'按钮,在'开发者选项'中关闭'不保留活动'功能.")  
                    .setNegativeButton("取消", new DialogInterface.OnClickListener() {  
                        @Override  
                        public void onClick(DialogInterface dialog, int which) {  
                            dialog.dismiss();  
                        }  
                    }).setPositiveButton("设置", new DialogInterface.OnClickListener() {  
                        @Override  
                        public void onClick(DialogInterface dialog, int which) {  
                            Intent intent = new Intent(  
                                    Settings.ACTION_APPLICATION_DEVELOPMENT_SETTINGS);  
                            startActivity(intent);  
                        }  
                    }).create();  
            dialog.show();  
        }  

Toast的最佳使用

    public class Util {
        private static Toast toast;
        public static void showToast(Context context, 
            String content) {
            if (toast == null) {
                toast = Toast.makeText(context,
                             content, 
                             Toast.LENGTH_SHORT);
            } else {
                toast.setText(content);
            }
            toast.show();
        }
    }