android笔记

开发中经常要去寻找一些常用的方法，做个整理方便以后观看

1.获取当前屏幕宽高：

DisplayMetrics metric = new DisplayMetrics();  getWindowManager().getDefaultDisplay().getMetrics(metric);  int width = metric.widthPixels;     // 屏幕宽度（像素）  int height = metric.heightPixels;   // 屏幕高度（像素）  float density = metric.density;      // 屏幕密度（0.75 / 1.0 / 1.5）  int densityDpi = metric.densityDpi;  // 屏幕密度DPI（120 / 160 / 240）  

2.在代码中设置如何设置dip

设置10dip的像素，第一个参数是类型，第二个参数是设置的值，第三个获取当前的尺度

int screenPaading = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 10, getResources().getDisplayMetrics())

3.在代码中设置TextView中画线和下划线

textView.getPaint().setFlags(Paint. UNDERLINE_TEXT_FLAG ); //下划线textView.getPaint().setAntiAlias(true);//抗锯齿textview.getPaint().setFlags(Paint. STRIKE_THRU_TEXT_FLAG); //中划线setFlags(Paint. STRIKE_THRU_TEXT_FLAG|Paint.ANTI_ALIAS_FLAG);  // 设置中划线并加清晰 textView.getPaint().setFlags(0); 

4.在代码中设置文字样式

//第一步，在assets目录下新建fonts目录，把ttf字体文件放到这。//第二步，程序中调用：AssetManager mgr=getAssets();//得到AssetManagerTypeface tf=Typeface.createFromAsset(mgr, "fonts/ttf.ttf");//根据路径得到Typefacetv.setTypeface(tf);//设置字体

5.代码设置textview部分变色

textview.setText(Html.fromHtml("text1<font color=red>需要改变的字体</font>"));

6.获取sdcard路径

    private String getSDCardPath() {          File sdcardDir = null;          // 判断SDCard是否存在          boolean sdcardExist = Environment.getExternalStorageState().equals(                  android.os.Environment.MEDIA_MOUNTED);          if (sdcardExist) {              sdcardDir = Environment.getExternalStorageDirectory();          }          return sdcardDir.toString();      } 

7.获取应用版本信息

/** * 获取版本号 * @return 当前应用的版本号 */public void getVersion() {    try {        PackageManager manager = this.getPackageManager();        PackageInfo info = manager.getPackageInfo(this.getPackageName(), 0);        versionName = info.versionName;        versionCode = info.versionCode;    } catch (Exception e) {        e.printStackTrace();    }}

8.判断指定service是否在运行

/** * 判断指定service是否已经在运行  * @param serviceName * @return */public  boolean isWorked(String serviceName) {    ActivityManager myManager = (ActivityManager)this.getSystemService(Context.ACTIVITY_SERVICE);    ArrayList<RunningServiceInfo> runningService = (ArrayList<RunningServiceInfo>) myManager.getRunningServices(30);    for(int i = 0 ; i<runningService.size();i++) {      if (runningService.get(i).service.getClassName().toString().equals(serviceName)) {      return true;        }}  

9.判断是否要影藏软键盘

InputMethodManager imm = (InputMethodManager)getSystemService(Context.INPUT_METHOD_SERVICE);if (imm.isActive()) {//隐藏软键盘imm.toggleSoftInput(0, InputMethodManager.HIDE_NOT_ALWAYS);} else if (!imm.isActive()) {//显示软键盘imm.toggleSoftInput(0, InputMethodManager.HIDE_NOT_ALWAYS);}

10.判断网络是否连接

//是否连接网络public boolean isNewworkConnect() {ConnectivityManager manager = (ConnectivityManager) mContext.getSystemService(Context.CONNECTIVITY_SERVICE);                NetworkInfo net = manager.getActiveNetworkInfo();                if (net != null && net.isConnected()) {                    return true;                }                 return false;}

11. andorid 布局文件声明引用自定义属性标签

xmlns:app="http://schemas.android.com/apk/res-auto"

12. andorid 文字适配多屏幕

res/values/dimens.xmlres/values-small/dimens.xmlres/values-normal/dimens.xmlres/values-large/dimens.xmlres/values-xlarge/dimens.xml

13. andorid 异步线程 回调细节

       //判断回调activity 是否已经被销毁       if (getActivity().isFinishing()) {             return;       }

14. andorid activity 跳转 不增加内存

Intent i = new Intent("com.you.yourActivityB");i.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);startActivity(i);

15. andorid 获取 内部存储路径（data/data）

getFilesDir() //获取内部存储路径或者String filename = "myfile";String string = "Hello world!";FileOutputStream outputStream;try {  outputStream = openFileOutput(filename, Context.MODE_PRIVATE);  outputStream.write(string.getBytes());  outputStream.close();} catch (Exception e) {  e.printStackTrace();}

16. andorid 发送邮件

Intent intent = new Intent(Intent.ACTION_SENDTO);intent.setType("message/rfc822");intent.putExtra(Intent.EXTRA_EMAIL, email);intent.setData(Uri.parse("mailto:"+email));intent.putExtra(Intent.EXTRA_SUBJECT, emailSubject);intent.putExtra(Intent.EXTRA_TEXT, emailContent);intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);intent.addFlags(Intent.FLAG_FROM_BACKGROUND);try {    startActivity(intent);} catch (android.content.ActivityNotFoundException e) {    // TODO Auto-generated catch block    e.printStackTrace();    Log.d("Email error:",e.toString());}

17. andorid 获取控件高宽

@Override    public void onWindowFocusChanged(boolean hasFocus) {        super.onWindowFocusChanged(hasFocus);    }    或    View.post(new Runnable() {        @Override        public void run() {                    }    });

18. andorid drawable.xml 多个背景切换

my_drawable.xml<level-list xmlns:android="http://schemas.android.com/apk/res/android">    <item android:maxLevel="0">        <shape android:shape="oval">            <solid android:color="@color/red"/>            <stroke android:width="1sp" android:color="@color/border" />        </shape>    </item>    <item android:maxLevel="1">        <shape android:shape="oval">            <solid android:color="@color/green"/>            <stroke android:width="1sp" android:color="@color/border" />        </shape>    </item>    <item android:maxLevel="2">        <shape android:shape="oval">            <solid android:color="@color/blue"/>            <stroke android:width="1sp" android:color="@color/blue" />        </shape>    </item></level-list>MyActivity.java// myView is a View (or a subclass of View) // with background set to R.drawable.my_drawablemyView.getBackground().setLevel(0); // Set color to redmyView.getBackground().setLevel(1); // Set color to greenmyView.getBackground().setLevel(2); // Set color to blue// myImageView is an ImageView with its source// set to R.drawable.my_drawablemyImageView.setImageLevel(0); // Set color to redmyImageView.setImageLevel(1); // Set color to greenmyImageView.setImageLevel(2); // Set color to blue

19. andorid 检测是否有符合条件的activity

Intent intent = new Intent(Intent.ACTION_VIEW);              intent.setDataAndType(Uri.parse(url), mimetype);              if (getPackageManager().resolveActivity(intent,                          PackageManager.MATCH_DEFAULT_ONLY) != null) {                  // someone knows how to handle this mime type with this scheme, don't download.                  try {                      startActivity(intent);                      return;                  } catch (ActivityNotFoundException ex) {                      if (Config.LOGD) {                          Log.d(LOGTAG, "activity not found for " + mimetype                                  + " over " + Uri.parse(url).getScheme(), ex);                      }                                        }  

20. andorid activity 监听返回键

    @Override    public void onBackPressed() {          }

21. andorid 判断存储空间是否足够

    public static boolean isEnoughSpace(long fileSize) { // 视频缓存是否有足够的空间        LogUtil.d(TAG, "fileSize=" + fileSize + ", 缓存可用=" + new File(getVideoCacheDir()).getUsableSpace());        return new File(getVideoCacheDir()).getUsableSpace() >= fileSize;    }

22. android 利用反射检查当前app的通知消息是否被关闭

public class NotificationsUtils {private static final String CHECK_OP_NO_THROW = "checkOpNoThrow";private static final String OP_POST_NOTIFICATION = "OP_POST_NOTIFICATION";public static boolean isNotificationEnabled() {    AppOpsManager mAppOps = (AppOpsManager) GlobalContext.getContext().getSystemService(Context.APP_OPS_SERVICE);    ApplicationInfo appInfo = GlobalContext.getContext().getApplicationInfo();    String pkg = GlobalContext.getContext().getApplicationContext().getPackageName();    int uid = appInfo.uid;    Class appOpsClass = null; /* Context.APP_OPS_MANAGER */    try {        appOpsClass = Class.forName(AppOpsManager.class.getName());        Method checkOpNoThrowMethod = appOpsClass.getMethod(CHECK_OP_NO_THROW, Integer.TYPE, Integer.TYPE, String.class);        Field opPostNotificationValue = appOpsClass.getDeclaredField(OP_POST_NOTIFICATION);        int value = (int)opPostNotificationValue.get(Integer.class);        return ((int)checkOpNoThrowMethod.invoke(mAppOps,value, uid, pkg) == AppOpsManager.MODE_ALLOWED);    } catch (ClassNotFoundException e) {        e.printStackTrace();    } catch (NoSuchMethodException e) {        e.printStackTrace();    } catch (NoSuchFieldException e) {        e.printStackTrace();    } catch (InvocationTargetException e) {        e.printStackTrace();    } catch (IllegalAccessException e) {        e.printStackTrace();    }    return false;}}

21. andorid 隐藏软件盘

View view = activity.getCurrentFocus();        if (view == null) {            view = new View(this);        }        //隐藏软键盘        InputMethodManager imm = (InputMethodManager)                getSystemService(Context.INPUT_METHOD_SERVICE);        imm.hideSoftInputFromWindow(view.getWindowToken(), InputMethodManager.HIDE_IMPLICIT_ONLY);

注意：在此activity 再 manifest中不能声明： android:windowSoftInputMode="stateHidden|adjustPan" 属性， 否则无效。

21. andorid NestedScrollView 内嵌 viewPager

    <android.support.v4.widget.NestedScrollView        android:layout_width="match_parent"        android:layout_height="match_parent"        android:fillViewport="true"        app:layout_behavior="@string/appbar_scrolling_view_behavior">            <android.support.v4.view.ViewPager                android:id="@+id/other_person_page_viewpage"                android:layout_width="match_parent"                android:layout_height="wrap_content">            </android.support.v4.view.ViewPager>    </android.support.v4.widget.NestedScrollView>

22. 跳转到指定app设置页面（用于设置权限）

                Intent intent = new Intent();                    intent.setAction(Settings.ACTION_APPLICATION_DETAILS_SETTINGS);                    Uri uri = Uri.fromParts("package", getPackageName(), null);                    intent.setData(uri);                    startActivity(intent);

23.String 便捷格式化

                        String month = String.format("%02d", (monthOfYear + 1)); //保留2位小数， example:  1 - 01, 10 - 10                        String day = String.format("%02d", dayOfMonth);