android 读写文件示例

在AndroidMainfest声明读写权限

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

在mainActiviry.java的onCreate动态弹窗请求一个权限

public void requestPermissionAll(){
	// 安卓版本检查，因为下面的checkSelfPermission以及shouldShowRequestPermissionRationale都是API23才开始支持的
	// API23是android6.0，即android M
	if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
		//权限检查
		if (checkSelfPermission(WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
			if (shouldShowRequestPermissionRationale(WRITE_EXTERNAL_STORAGE)) {
				requestPermissions(new String[]{WRITE_EXTERNAL_STORAGE}, 100);
			} else {
				requestPermissions(new String[]{WRITE_EXTERNAL_STORAGE}, 100);
			}
		}
	}
}

这是一个java的代码,在Download目录里面写一个文件作为示范

File file = new File(Environment.getExternalStoragePublicDirectory(
                            Environment.DIRECTORY_DOWNLOADS) + "/test.log");
//写一个文本
try {
	out = new FileOutputStream(file);
	out.write("我是字符串".getBytes());
	out.flush();
	out.close();
} catch (Exception e) {
	e.printStackTrace();
}

写了肯定是要读出来吧

String readme="";
try {
	in = new FileInputStream(file);
	//使用缓冲来读
	byte[] buf = new byte[1024];//每1024字节读一次
	StringBuilder builder = new StringBuilder();
	while (in.read(buf) != -1) {
		builder.append(new String(buf).trim());
	}
	readme = builder.toString();
} catch (Exception e) {
	e.printStackTrace();
}