android 怎么监听截屏

要在Android中截屏，您可以使用以下方法：

1. 使用ContentObserver类媒体库的变化，当媒体库中添加了新的图片时，判断该图片是否是截屏图片。您可以在onCreate()方法中注册ContentObserver，在onDestroy()方法中注销它。以下是一个示例代码：

```java

public class ScreenshotObserver extends ContentObserver {

private static final String TAG = "ScreenshotObserver";

private static final String MEDIA_EXTERNAL_CONTENT_URI = "content://media/external/images/media";

private Context mContext;

private String mLastModifiedPath;

public ScreenshotObserver(Context context) {

super(null);

mContext = context;

}

@Override

public void onChange(boolean selfChange, Uri uri) {

super.onChange(selfChange, uri);

Log.d(TAG, "Content changed: " + uri.toString());

// 只处理媒体库中添加的图片

if (uri.toString().startsWith(MEDIA_EXTERNAL_CONTENT_URI)) {

String newPath = getFilePathFromContentUri(mContext, uri);

// 检查图片是否是截屏图片

if (isScreenshot(newPath)) {

Log.d(TAG, "Screenshot taken: " + newPath);

// 处理截屏图片

}

mLastModifiedPath = newPath;

}

}

private boolean isScreenshot(String path) {

// 检查是否是截屏图片的逻辑，例如判断文件名、文件夹等

// 这里只是个示例，您需要根据实际情况进行判断

return path != null && path.contains("Screenshot");

}

private String getFilePathFromContentUri(Context context, Uri uri) {

String filePath = null;

String[] projection = {MediaStore.Images.Media.DATA};

Cursor cursor = context.getContentResolver().query(uri, projection, null, null, null);

if (cursor != null && cursor.moveToFirst()) {

filePath = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA));

cursor.close();

}

return filePath;

}

}

```

然后在Activity中注册和注销ContentObserver：

```java

public class MainActivity extends AppCompatActivity {

private ScreenshotObserver mScreenshotObserver;

private static final Uri MEDIA_EXTERNAL_CONTENT_URI = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

mScreenshotObserver = new ScreenshotObserver(this);

getContentResolver().registerContentObserver(MEDIA_EXTERNAL_CONTENT_URI, true, mScreenshotObserver);

}

@Override

protected void onDestroy() {

getContentResolver().unregisterContentObserver(mScreenshotObserver);

super.onDestroy();

}

}

```

2. 使用FileObserver类指定目录的变化，当该目录中添加了新的文件时，判断文件是否是截屏图片。同样，您可以在onCreate()方法中启动FileObserver，在onDestroy()方法中停止它。以下是一个示例代码：

```java

public class ScreenshotObserver extends FileObserver {

private static final String TAG = "ScreenshotObserver";

private static final String SCREENSHOT_DIR_PATH = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES) + "/Screenshots";

private String mLastModifiedPath;

public ScreenshotObserver() {

super(SCREENSHOT_DIR_PATH, FileObserver.CLOSE_WRITE);

}

@Override

public void onEvent(int event, String path) {

Log.d(TAG, "File changed: " + path);

if (event == FileObserver.CLOSE_WRITE) {

String newPath = SCREENSHOT_DIR_PATH + "/" + path;

// 检查文件是否是截屏图片

if (isScreenshot(newPath)) {

Log.d(TAG, "Screenshot taken: " + newPath);

// 处理截屏图片

}

mLastModifiedPath = newPath;

}

}

private boolean isScreenshot(String path) {

// 检查是否是截屏图片的逻辑，例如判断文件名、文件夹等

// 这里只是个示例，您需要根据实际情况进行判断

return path != null && path.contains("Screenshot");

}

}

```

然后在Activity中启动和停止FileObserver：

```java

public class MainActivity extends AppCompatActivity {

private ScreenshotObserver mScreenshotObserver;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

mScreenshotObserver = new ScreenshotObserver();

mScreenshotObserver.startWatching();

}

@Override

protected void onDestroy() {

mScreenshotObserver.stopWatching();

super.onDestroy();

}

}

```

无论哪种方法，当检测到截屏时，您可以执行自己的处理逻辑，例如显示一个提示框或发送一个广播。但请注意，这两种方法都无法root权限下进行截屏的情况。