检查外部存储的状态
/**
* 外部存储的状态
*
* @return
*/
public boolean isExternalStorageWritable() {
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) {
return true;
}
Log.e("state=", "" + state);
return false;
}
向外部存储写入字符串、图片
private void writeStringToFile(String str) {
if (!isExternalStorageWritable()) {
return;
}
File dir = getExternalFilesDir("text");
Log.e(TAG, "writeStringToFile: dir = " + dir.getAbsolutePath());
if (!dir.exists()) {
dir.mkdirs();
}
File file = new File(dir, "str.txt");
if (file.exists()) {
file.delete();
}
FileOutputStream fos = null;
BufferedOutputStream bos = null;
try {
file.createNewFile();
fos = new FileOutputStream(file);
bos = new BufferedOutputStream(fos);
bos.write(str.getBytes());
bos.close();
fos.close();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (bos != null) {
bos.close();
}
if (fos != null) {
fos.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
private void writeImageToFile(Bitmap bitmap) {
if (!isExternalStorageWritable()) {
return;
}
File dir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);
Log.e(TAG, "writeImageToFile: dir = " + dir.getAbsolutePath());
if (!dir.exists()) {
dir.mkdirs();
}
File file = new File(dir, "ic.png");
if (file.exists()) {
file.delete();
}
FileOutputStream fos = null;
BufferedOutputStream bos = null;
try {
file.createNewFile();
fos = new FileOutputStream(file);
bos = new BufferedOutputStream(fos);
bitmap.compress(Bitmap.CompressFormat.PNG, 100, bos);
bos.flush();
bos.close();
fos.close();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (bos != null) {
bos.close();
}
if (fos != null) {
fos.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
读取外部存储中的文本文件，图片文件
private String readStringFromFile() {
if (!isExternalStorageWritable()) {
return null;
}
File dir = getExternalFilesDir(Environment.DIRECTORY_DOCUMENTS);
Log.e(TAG, "readStringFromFile: dir = " + dir.getAbsolutePath());
if (!dir.exists()) {
return null;
}
File file = new File(dir, "str.txt");
if (!file.exists()) {
return null;
}
FileInputStream fis = null;
InputStreamReader isr = null;
BufferedReader br = null;
StringBuffer sb = new StringBuffer();
try {
fis = new FileInputStream(file);//通过字节流获取
isr = new InputStreamReader(fis);
br = new BufferedReader(isr);
String line;
sb.append(br.readLine());
while ((line = br.readLine()) != null) {
sb.append("\n" + line);
}
br.close();
isr.close();
fis.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (br != null) {
br.close();
}
if (isr != null) {
isr.close();
}
if (fis != null) {
fis.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return sb.toString();
}
private Bitmap readBitmapFromFile() {
if (!isExternalStorageWritable()) {
return null;
}
File dir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);
Log.e(TAG, "readBitmapFromFile: dir = " + dir.getAbsolutePath());
if (!dir.exists()) {
return null;
}
File file = new File(dir, "ic.png");
if (!file.exists()) {
return null;
}
FileInputStream fis = null;
BufferedInputStream bis = null;
Bitmap bitmap = null;
try {
fis = new FileInputStream(file);
bis = new BufferedInputStream(fis);
bitmap = BitmapFactory.decodeStream(bis);
bis.close();
fis.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (bis != null) {
bis.close();
}
if (fis != null) {
fis.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return bitmap;
}
从文件中读取数据
/**
* 从文件中读取数据
*
* @param context
* @return
* @throws IOException
*/
public static String readFile(Context context) throws IOException {
StringBuilder sb = new StringBuilder("");
File file = new File(context.getExternalFilesDir("voice") + "/voice.pcm");
//打开文件输入流
FileInputStream inputStream = new FileInputStream(file);
byte[] buffer = new byte[1024];
int len = inputStream.read(buffer);
//读取文件内容
while (len > 0) {
sb.append(new String(buffer, 0, len));
//继续将数据放到buffer中
len = inputStream.read(buffer);
}
//关闭输入流
inputStream.close();
return sb.toString();
}
如何读取 assets 文件夹中的文件
参考：
AssetManager
assets 文件夹用于存储应用需要的文件，在安装后可直接从其中读取使用或者写入本地存储中
Android Studio 默认不建立该文件夹，可以手动新建 : app -> src -> main -> assets
或者，右键 main -> New -> Folder -> Assets Folder
AssetManager 对象可以直接访问该文件夹：
获取方法：
AssetManager assetManager = this.getApplicationContext().getAssets();
使用函数 open 可以打开 assets 文件夹中对象，返回一个 InputStream 对象：
open
获取方法：
inputStream = assetManager.open("label.txt");
读取assets中文本文件
private String readStringFromAssets() {
AssetManager assetManager = this.getApplicationContext().getAssets();
InputStream inputStream = null;
InputStreamReader isr = null;
BufferedReader br = null;
StringBuffer sb = new StringBuffer();
try {
inputStream = assetManager.open("label.txt");
isr = new InputStreamReader(inputStream);
br = new BufferedReader(isr);
sb.append(br.readLine());
String line = null;
while ((line = br.readLine()) != null) {
sb.append("\n" + line);
}
br.close();
isr.close();
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (br != null) {
br.close();
}
if (isr != null) {
isr.close();
}
if (inputStream != null) {
inputStream.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return sb.toString();
}
读取assets中文件，并写入本地
private boolean readDataFromAssets() {
if (!isExternalStorageWritable()) {
return false;
}
InputStream inputStream = null;
FileOutputStream fos = null;
BufferedOutputStream bos = null;
File dir = getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS);
Log.e(TAG, "readDataFromAssets: dir = " + dir.getAbsolutePath());
if (!dir.exists()) {
dir.mkdirs();
}
try {
inputStream = getAssets().open("app-debug.apk");
File file = new File(dir, "app-debug.apk");
if (file.exists()) {
file.delete();
}
file.createNewFile();
fos = new FileOutputStream(file);
bos = new BufferedOutputStream(fos);
byte[] bytes = new byte[1024];
while (inputStream.read(bytes) > 0) {
bos.write(bytes, 0, bytes.length);
}
inputStream.close();
bos.close();
fos.close();
} catch (IOException e) {
e.printStackTrace();
return false;
} finally {
try {
if (inputStream != null) {
inputStream.close();
}
if (bos != null) {
bos.close();
}
if (fos != null) {
fos.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return true;
}
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