我在Android M中创建文件时遇到问题。
我在 Android 6.0.1 中使用 Nexus 9 。然后我在我的项目中设置如下：
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
android {
defaultConfig {
targetSdkVersion 23
...
}
}
public class MainActivity extends AppCompatActivity {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
String storagePath = Environment.getExternalStorageDirectory().getAbsolutePath();
String rootPath = storagePath + "/test";
String fileName = "/test.zip";
File root = new File(rootPath);
if(!root.mkdirs()) {
Log.i("Test", "This path is already exist: " + root.getAbsolutePath());
}
File file = new File(rootPath + fileName);
try {
if (!file.createNewFile()) {
Log.i("Test", "This file is already exist: " + file.getAbsolutePath());
}
} catch (Exception e) {
e.printStackTrace();
}
}
构建成功并启动了应用程序，但我得到了这样的异常消息：
01-07 18:13:40.669 18027-18027/com.sample.myapplication W/System.err: java.io.IOException: open failed: ENOENT (No such file or directory)
01-07 18:13:40.669 18027-18027/com.sample.myapplication W/System.err: at java.io.File.createNewFile(File.java:939)
01-07 18:13:40.669 18027-18027/com.sample.myapplication W/System.err: at com.sample.myapplication.MainActivity.onCreate(MainActivity.java:36)
01-07 18:13:40.670 18027-18027/com.sample.myapplication W/System.err: at android.app.Activity.performCreate(Activity.java:6251)
01-07 18:13:40.670 18027-18027/com.sample.myapplication W/System.err: at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
01-07 18:13:40.670 18027-18027/com.sample.myapplication W/System.err: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
01-07 18:13:40.670 18027-18027/com.sample.myapplication W/System.err: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
01-07 18:13:40.670 18027-18027/com.sample.myapplication W/System.err: at android.app.ActivityThread.-wrap11(ActivityThread.java)
01-07 18:13:40.671 18027-18027/com.sample.myapplication W/System.err: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
01-07 18:13:40.671 18027-18027/com.sample.myapplication W/System.err: at android.os.Handler.dispatchMessage(Handler.java:102)
01-07 18:13:40.671 18027-18027/com.sample.myapplication W/System.err: at android.os.Looper.loop(Looper.java:148)
01-07 18:13:40.671 18027-18027/com.sample.myapplication W/System.err: at android.app.ActivityThread.main(ActivityThread.java:5417)
01-07 18:13:40.671 18027-18027/com.sample.myapplication W/System.err: at java.lang.reflect.Method.invoke(Native Method)
01-07 18:13:40.671 18027-18027/com.sample.myapplication W/System.err: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
01-07 18:13:40.671 18027-18027/com.sample.myapplication W/System.err: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
01-07 18:13:40.671 18027-18027/com.sample.myapplication W/System.err: Caused by: android.system.ErrnoException: open failed: ENOENT (No such file or directory)
01-07 18:13:40.671 18027-18027/com.sample.myapplication W/System.err: at libcore.io.Posix.open(Native Method)
01-07 18:13:40.671 18027-18027/com.sample.myapplication W/System.err: at libcore.io.BlockGuardOs.open(BlockGuardOs.java:186)
01-07 18:13:40.671 18027-18027/com.sample.myapplication W/System.err: at java.io.File.createNewFile(File.java:932)
01-07 18:13:40.671 18027-18027/com.sample.myapplication W/System.err: ... 13 more
我该如何解决这个问题？我不会抓住我想念的东西......
请帮忙。
答案 0 :(得分：5)
我编辑我的代码：添加＆＃34;请求检查权限＆＃34;代码onCreate。
谢谢，拉尔托。
我不了解运行时权限。
我解决了这样的异常：
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
/* Request user permissions in runtime */
ActivityCompat.requestPermissions(MainActivity.this,
new String[] {
Manifest.permission.READ_EXTERNAL_STORAGE,
Manifest.permission.WRITE_EXTERNAL_STORAGE
},
100);
/* Request user permissions in runtime */
String storagePath = Environment.getExternalStorageDirectory().getAbsolutePath();
String rootPath = storagePath + "/test";
String fileName = "/test.zip";
File root = new File(rootPath);
if(!root.mkdirs()) {
Log.i("Test", "This path is already exist: " + root.getAbsolutePath());
}
File file = new File(rootPath + fileName);
try {
int permissionCheck = ContextCompat.checkSelfPermission(MainActivity.this, android.Manifest.permission.WRITE_EXTERNAL_STORAGE);
if (permissionCheck == PackageManager.PERMISSION_GRANTED) {
if (!file.createNewFile()) {
Log.i("Test", "This file is already exist: " + file.getAbsolutePath());
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
@TargetApi(23)
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
switch (requestCode) {
case 100:
if (grantResults.length > 0
|| grantResults[0] == PackageManager.PERMISSION_GRANTED
|| grantResults[1] == PackageManager.PERMISSION_GRANTED) {
/* User checks permission. */
} else {
Toast.makeText(MainActivity.this, "Permission is denied.", Toast.LENGTH_SHORT).show();
finish();
}
//return; // delete.
}
}
}
有效！
答案 1 :(得分：0)
我遇到了同样的问题。我在file.createNewFile上遇到了IOException。仔细研究一下这个例外就会发现它是由于“权限被拒绝”。我正在写我的getFilesDir，所以我不需要在android清单中完成这个任务。我当然为外部存储添加了READ和WRITE权限，当然，这并没有解决问题。
我一直在使用带有sdk 26的NEXUS 6仿真器测试代码。在不更改任何代码的情况下，我尝试使用带有sdk 26的PIXEL C仿真器进行测试，但问题没有发生。所以我的Nexus 6仿真器似乎有些问题。
我怀疑这并不总是一个问题，而且这个模拟器实例已损坏，但我还没有验证过。我确实花时间查看我创建文件的目录的linux文件权限，并将其报告为“drwxrwxrwx”，这是正确的。我将添加我已经实现了一个FileProvider，其中包含我正在尝试创建新文件的目录的路径。我使用的代码看起来就像Kae10显示的代码。
我在UnixFileSystem中将问题追溯到此代码：
public boolean createFileExclusively(String path) throws IOException {
BlockGuard.getThreadPolicy().onWriteToDisk();
return createFileExclusively0(path);
}
从createFileExlussively0抛出异常，我无法调试。我没有进一步研究这个问题（即1.）会删除avd实例并重新创建它的帮助，我的猜测可能是，2。）是否有我应该使用的后续系统映像？）