Context类简单解析
Context上下文对象
通过它可以获取应用整体信息的接口：
直接实现类
ContextWrapper
MockContext
间接实现类：
ContextThemeWrapper acticity就是集成这个类 所有activity里面获取相关资源的api全部从这个地方来的
常用api
Context类简单介绍
1：提供创建文件的模式 eg：public static final int MODE_PRIVATE = 0x0000;
2：提供bindService的相关模式 public static final int BIND_AUTO_CREATE = 0x0001;
3：获取sharepreferense存储数据 getSharedPreferences
4：数据库操作api
5：getAssets()
6：getResources();
7：getPackageManager()
8：getContentResolver()
9：getMainLooper()
10：getApplicationContext()
11： public final CharSequence getText(@StringRes int resId) {
return getResources().getText(resId);
}
12：public final int getColor(int id) {
return getResources().getColor(id, getTheme());
}
13：public final Drawable getDrawable(int id) {
return getResources().getDrawable(id, getTheme());
}
14：public final ColorStateList getColorStateList(int id) {
return getResources().getColorStateList(id, getTheme());
}
15：public abstract void setTheme(@StyleRes int resid);
16：public final TypedArray obtainStyledAttributes(@StyleableRes int[] attrs) {
return getTheme().obtainStyledAttributes(attrs);
}
17：public final TypedArray obtainStyledAttributes(
@StyleRes int resid, @StyleableRes int[] attrs) throws Resources.NotFoundException {
return getTheme().obtainStyledAttributes(resid, attrs);
}
18：public final TypedArray obtainStyledAttributes(
AttributeSet set, @StyleableRes int[] attrs) {
return getTheme().obtainStyledAttributes(set, attrs, 0, 0);
}
19：public abstract ClassLoader getClassLoader();
20：public abstract String getPackageName();
public abstract String getBasePackageName();
21：public abstract ApplicationInfo getApplicationInfo();
22：public abstract String getPackageResourcePath();
23：public abstract String getPackageCodePath();
24：public abstract File getSharedPrefsFile(String name);
25：public abstract SharedPreferences getSharedPreferences(String name,
int mode);
26：/**
* Open a private file associated with this Context's application package
* for reading.
*
* @param name The name of the file to open; can not contain path
* separators.
*
* @return The resulting {@link FileInputStream}.
*
* @see #openFileOutput
* @see #fileList
* @see #deleteFile
* @see java.io.FileInputStream#FileInputStream(String)
*/
public abstract FileInputStream openFileInput(String name)
throws FileNotFoundException;
27：/**
* Open a private file associated with this Context's application package
* for writing. Creates the file if it doesn't already exist.
*
*
No permissions are required to invoke this method, since it uses internal
* storage.
*
* @param name The name of the file to open; can not contain path
* separators.
* @param mode Operating mode. Use 0 or {@link #MODE_PRIVATE} for the
* default operation, {@link #MODE_APPEND} to append to an existing file,
* {@link #MODE_WORLD_READABLE} and {@link #MODE_WORLD_WRITEABLE} to control
* permissions.
*
* @return The resulting {@link FileOutputStream}.
*
* @see #MODE_APPEND
* @see #MODE_PRIVATE
* @see #MODE_WORLD_READABLE
* @see #MODE_WORLD_WRITEABLE
* @see #openFileInput
* @see #fileList
* @see #deleteFile
* @see java.io.FileOutputStream#FileOutputStream(String)
*/
public abstract FileOutputStream openFileOutput(String name, int mode)
throws FileNotFoundException;
28：/**
* Delete the given private file associated with this Context's
* application package.
*
* @param name The name of the file to delete; can not contain path
* separators.
*
* @return {@code true} if the file was successfully deleted; else
* {@code false}.
*
* @see #openFileInput
* @see #openFileOutput
* @see #fileList
* @see java.io.File#delete()
*/
public abstract boolean deleteFile(String name);
29：public abstract File getFileStreamPath(String name);
30：/**
* Returns the absolute path to the directory on the filesystem where
* files created with {@link #openFileOutput} are stored.
*
*
No permissions are required to read or write to the returned path, since this
* path is internal storage.
*
* @return The path of the directory holding application files.
*
* @see #openFileOutput
* @see #getFileStreamPath
* @see #getDir
*/
public abstract File getFilesDir();
31：/**
* Returns the absolute path to the directory on the primary external filesystem
* (that is somewhere on {@link android.os.Environment#getExternalStorageDirectory()
* Environment.getExternalStorageDirectory()}) where the application can
* place persistent files it owns. These files are internal to the
* applications, and not typically visible to the user as media.
*
*
This is like {@link #getFilesDir()} in that these
* files will be deleted when the application is uninstalled, however there
* are some important differences:
*
*
- External files are not always available: they will disappear if the
* user mounts the external storage on a computer or removes it. See the
* APIs on {@link android.os.Environment} for information in the storage state.
* - There is no security enforced with these files. For example, any application
* holding {@link android.Manifest.permission#WRITE_EXTERNAL_STORAGE} can write to
* these files.
*
*
*
*
Starting in {@link android.os.Build.VERSION_CODES#KITKAT}, no permissions
* are required to read or write to the returned path; it's always
* accessible to the calling app. This only applies to paths generated for
* package name of the calling application. To access paths belonging
* to other packages, {@link android.Manifest.permission#WRITE_EXTERNAL_STORAGE}
* and/or {@link android.Manifest.permission#READ_EXTERNAL_STORAGE} are required.
*
*
On devices with multiple users (as described by {@link UserManager}),
* each user has their own isolated external storage. Applications only
* have access to the external storage for the user they're running as.
*
*
Here is an example of typical code to manipulate a file in
* an application's private storage:
*
* {@sample development/samples/ApiDemos/src/com/example/android/apis/content/ExternalStorage.java
* private_file}
*
*
If you supply a non-null type to this function, the returned
* file will be a path to a sub-directory of the given type. Though these files
* are not automatically scanned by the media scanner, you can explicitly
* add them to the media database with
* {@link android.media.MediaScannerConnection#scanFile(Context, String[], String[],
* android.media.MediaScannerConnection.OnScanCompletedListener)
* MediaScannerConnection.scanFile}.
* Note that this is not the same as
* {@link android.os.Environment#getExternalStoragePublicDirectory
* Environment.getExternalStoragePublicDirectory()}, which provides
* directories of media shared by all applications. The
* directories returned here are
* owned by the application, and their contents will be removed when the
* application is uninstalled. Unlike
* {@link android.os.Environment#getExternalStoragePublicDirectory
* Environment.getExternalStoragePublicDirectory()}, the directory
* returned here will be automatically created for you.
*
*
Here is an example of typical code to manipulate a picture in
* an application's private storage and add it to the media database:
*
* {@sample development/samples/ApiDemos/src/com/example/android/apis/content/ExternalStorage.java
* private_picture}
*
* @param type The type of files directory to return. May be null for
* the root of the files directory or one of
* the following Environment constants for a subdirectory:
* {@link android.os.Environment#DIRECTORY_MUSIC},
* {@link android.os.Environment#DIRECTORY_PODCASTS},
* {@link android.os.Environment#DIRECTORY_RINGTONES},
* {@link android.os.Environment#DIRECTORY_ALARMS},
* {@link android.os.Environment#DIRECTORY_NOTIFICATIONS},
* {@link android.os.Environment#DIRECTORY_PICTURES}, or
* {@link android.os.Environment#DIRECTORY_MOVIES}.
*
* @return The path of the directory holding application files
* on external storage. Returns null if external storage is not currently
* mounted so it could not ensure the path exists; you will need to call
* this method again when it is available.
*
* @see #getFilesDir
* @see android.os.Environment#getExternalStoragePublicDirectory
*/
@Nullable
public abstract File getExternalFilesDir(@Nullable String type);
32：public abstract File[] getExternalFilesDirs(String type);
33：public abstract File getCacheDir();
34：@Nullable
public abstract File getExternalCacheDir();
35：public abstract File[] getExternalCacheDirs();
36：public abstract SQLiteDatabase openOrCreateDatabase(String name,
int mode, CursorFactory factory);
37：public abstract boolean deleteDatabase(String name);
38：public abstract File getDatabasePath(String name);
39：@Deprecated
public abstract Drawable getWallpaper();
40： @Deprecated
public abstract void setWallpaper(Bitmap bitmap) throws IOException;
41：public abstract void startActivity(Intent intent);
42：public abstract void sendBroadcast(Intent intent);
43：public abstract void sendBroadcast(Intent intent,
@Nullable String receiverPermission);
44：@SystemApi
public abstract void sendBroadcast(Intent intent,
@Nullable String receiverPermission,
@Nullable Bundle options);
45：public abstract void sendOrderedBroadcast(Intent intent,
@Nullable String receiverPermission);
还有其他同构方法
46：@Deprecated
public abstract void sendStickyBroadcast(Intent intent);
@Deprecated
public abstract void sendStickyOrderedBroadcast(Intent intent,
BroadcastReceiver resultReceiver,
@Nullable Handler scheduler, int initialCode, @Nullable String initialData,
@Nullable Bundle initialExtras);
@Deprecated
public abstract void removeStickyBroadcast(Intent intent);
47：@Nullable
public abstract Intent registerReceiver(@Nullable BroadcastReceiver receiver,
IntentFilter filter);
@Nullable
public abstract Intent registerReceiver(BroadcastReceiver receiver,
IntentFilter filter, @Nullable String broadcastPermission,
@Nullable Handler scheduler);
public abstract void unregisterReceiver(BroadcastReceiver receiver);
48：@Nullable
public abstract ComponentName startService(Intent service);
public abstract boolean stopService(Intent service);
public abstract boolean bindService(Intent service, @NonNull ServiceConnection conn,
@BindServiceFlags int flags);
public abstract void unbindService(@NonNull ServiceConnection conn);
49：public abstract Object getSystemService(@ServiceName @NonNull String name);
public static final String POWER_SERVICE = "power";
各类service的名称都在Context类里面以静态常量的形式存在
50：@CheckResult(suggest="#enforcePermission(String,int,int,String)")
@PackageManager.PermissionResult
public abstract int checkPermission(@NonNull String permission, int pid, int uid);
/** @hide */
@PackageManager.PermissionResult
public abstract int checkPermission(@NonNull String permission, int pid, int uid,
IBinder callerToken);
@CheckResult(suggest="#enforceCallingPermission(String,String)")
@PackageManager.PermissionResult
public abstract int checkCallingPermission(@NonNull String permission);
@PackageManager.PermissionResult
public abstract int checkSelfPermission(@NonNull String permission);
public abstract void enforcePermission(
@NonNull String permission, int pid, int uid, @Nullable String message);
public abstract void grantUriPermission(String toPackage, Uri uri,
@Intent.GrantUriMode int modeFlags);
@CheckResult(suggest="#enforceUriPermission(Uri,int,int,String)")
public abstract int checkUriPermission(Uri uri, int pid, int uid,
@Intent.AccessUriMode int modeFlags);
51：public abstract int getUserId();