从下载文件夹读取文本文件失败

Question

当我单击加载按钮时，文件内容未加载到 TextView 中 在

BufferedReader

方法中上传

ReadText

中的文件时似乎出现错误。

这是来自“Logcat”的图片

public class MainActivity extends AppCompatActivity 

    private static final int READ_REQUEST_CODE = 42;
    private static final int PERMISSION_REQUEST_STORAGE = 1000;

    Button b_load;
    TextView tv_output;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED) {
            requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, PERMISSION_REQUEST_STORAGE);
        }


        b_load = findViewById(R.id.b_load);
        tv_output = findViewById(R.id.tv_output);

        b_load.setOnClickListener(v -> performFileSearch());
    }

    private String readText(String input) {
        File file = new File(Environment.getExternalStorageDirectory(), input);
        StringBuilder text = new StringBuilder();
        try {
            BufferedReader br = new BufferedReader(new FileReader(file));
            String line;
            while ((line = br.readLine()) != null) {
                text.append(line);
                text.append("\n");
            }
            br.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return text.toString();
    }

    private void performFileSearch() {
        Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        intent.setType("text/*");
        startActivityForResult(intent, READ_REQUEST_CODE);
    }

    @SuppressLint("MissingSuperCall")
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == READ_REQUEST_CODE && resultCode == Activity.RESULT_OK) {
            if (data != null) {
                Uri uri = data.getData();
                String path = uri.getPath();
                path = path.substring(path.indexOf(":") + 1);
                Toast.makeText(this, "" + path, Toast.LENGTH_SHORT).show();
                tv_output.setText(readText(path));
            }
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (requestCode == PERMISSION_REQUEST_STORAGE) {
            if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this, "Permission granted", Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(this, "Permission not granted", Toast.LENGTH_SHORT).show();
                finish();
            }
        }
    }
}

2020-12-21 21:40:11.722 10679-10679/? I/downloadfilecs: Not late-enabling -Xcheck:jni (already on)
2020-12-21 21:40:11.860 10679-10679/? E/downloadfilecs: Unknown bits set in runtime_flags: 0x8000
2020-12-21 21:40:11.877 10679-10679/? W/downloadfilecs: Unexpected CPU variant for X86 using defaults: x86
2020-12-21 21:40:12.727 10679-10679/com.gsbitdz.downloadfilecsv W/RenderThread: type=1400 audit(0.0:321): avc: denied { write } for name="property_service" dev="tmpfs" ino=6875 scontext=u:r:untrusted_app:s0:c149,c256,c512,c768 tcontext=u:object_r:property_socket:s0 tclass=sock_file permissive=0 app=com.gsbitdz.downloadfilecsv
2020-12-21 21:40:12.737 10679-10708/com.gsbitdz.downloadfilecsv D/libEGL: Emulator has host GPU support, qemu.gles is set to 1.
2020-12-21 21:40:12.737 10679-10708/com.gsbitdz.downloadfilecsv W/libc: Unable to set property "qemu.gles" to "1": connection failed; errno=13 (Permission denied)
2020-12-21 21:40:12.880 10679-10679/com.gsbitdz.downloadfilecsv W/downloadfilecs: Verification of void androidx.fragment.app.FragmentActivity.<init>() took 135.663ms
2020-12-21 21:40:13.041 10679-10708/com.gsbitdz.downloadfilecsv D/libEGL: loaded /vendor/lib/egl/libEGL_emulation.so
2020-12-21 21:40:13.238 10679-10708/com.gsbitdz.downloadfilecsv D/libEGL: loaded /vendor/lib/egl/libGLESv1_CM_emulation.so
2020-12-21 21:40:13.274 10679-10708/com.gsbitdz.downloadfilecsv D/libEGL: loaded /vendor/lib/egl/libGLESv2_emulation.so
2020-12-21 21:40:14.048 10679-10679/com.gsbitdz.downloadfilecsv W/downloadfilecs: Accessing hidden method Landroid/view/View;->computeFitSystemWindows(Landroid/graphics/Rect;Landroid/graphics/Rect;)Z (greylist, reflection, allowed)
2020-12-21 21:40:14.050 10679-10679/com.gsbitdz.downloadfilecsv W/downloadfilecs: Accessing hidden method Landroid/view/ViewGroup;->makeOptionalFitsSystemWindows()V (greylist, reflection, allowed)
2020-12-21 21:40:14.350 10679-10706/com.gsbitdz.downloadfilecsv D/HostConnection: HostConnection::get() New Host Connection established 0xe194e190, tid 10706
2020-12-21 21:40:14.392 10679-10706/com.gsbitdz.downloadfilecsv D/HostConnection: HostComposition ext ANDROID_EMU_CHECKSUM_HELPER_v1 ANDROID_EMU_dma_v1 ANDROID_EMU_direct_mem ANDROID_EMU_host_composition_v1 ANDROID_EMU_host_composition_v2 ANDROID_EMU_YUV420_888_to_NV21 ANDROID_EMU_YUV_Cache ANDROID_EMU_async_unmap_buffer GL_OES_EGL_image_external_essl3 GL_OES_vertex_array_object GL_KHR_texture_compression_astc_ldr ANDROID_EMU_gles_max_version_3_0 
2020-12-21 21:40:14.443 10679-10706/com.gsbitdz.downloadfilecsv D/EGL_emulation: eglCreateContext: 0xe191a120: maj 3 min 0 rcv 3
2020-12-21 21:40:14.455 10679-10706/com.gsbitdz.downloadfilecsv D/EGL_emulation: eglMakeCurrent: 0xe191a120: ver 3 0 (tinfo 0xe190f3a0)
2020-12-21 21:40:14.557 10679-10706/com.gsbitdz.downloadfilecsv W/Gralloc3: mapper 3.x is not supported
2020-12-21 21:40:14.560 10679-10706/com.gsbitdz.downloadfilecsv D/HostConnection: createUnique: call
2020-12-21 21:40:14.561 10679-10706/com.gsbitdz.downloadfilecsv D/HostConnection: HostConnection::get() New Host Connection established 0xe194e2d0, tid 10706
2020-12-21 21:40:14.609 10679-10706/com.gsbitdz.downloadfilecsv D/HostConnection: HostComposition ext ANDROID_EMU_CHECKSUM_HELPER_v1 ANDROID_EMU_dma_v1 ANDROID_EMU_direct_mem ANDROID_EMU_host_composition_v1 ANDROID_EMU_host_composition_v2 ANDROID_EMU_YUV420_888_to_NV21 ANDROID_EMU_YUV_Cache ANDROID_EMU_async_unmap_buffer GL_OES_EGL_image_external_essl3 GL_OES_vertex_array_object GL_KHR_texture_compression_astc_ldr ANDROID_EMU_gles_max_version_3_0 
2020-12-21 21:40:14.610 10679-10706/com.gsbitdz.downloadfilecsv D/eglCodecCommon: allocate: Ask for block of size 0x1000
2020-12-21 21:40:14.610 10679-10706/com.gsbitdz.downloadfilecsv D/eglCodecCommon: allocate: ioctl allocate returned offset 0x3ff807000 size 0x2000
2020-12-21 21:40:14.652 10679-10706/com.gsbitdz.downloadfilecsv D/EGL_emulation: eglMakeCurrent: 0xe191a120: ver 3 0 (tinfo 0xe190f3a0)
2020-12-21 21:40:14.792 10679-10690/com.gsbitdz.downloadfilecsv I/downloadfilecs: NativeAlloc concurrent copying GC freed 2178(194KB) AllocSpace objects, 1(20KB) LOS objects, 51% free, 1449KB/2985KB, paused 1.088ms total 156.156ms
2020-12-21 21:40:15.694 10679-10706/com.gsbitdz.downloadfilecsv I/OpenGLRenderer: Davey! duration=1382ms; Flags=1, IntendedVsync=143238159428185, Vsync=143238159428185, OldestInputEvent=9223372036854775807, NewestInputEvent=0, HandleInputStart=143238165820360, AnimationStart=143238165943520, PerformTraversalsStart=143238166044870, DrawStart=143238477194280, SyncQueued=143238505988740, SyncStart=143238512527730, IssueDrawCommandsStart=143238512771480, SwapBuffers=143239375546860, FrameCompleted=143239548621940, DequeueBufferDuration=636000, QueueBufferDuration=1062000, 
2020-12-21 21:40:16.126 10679-10679/com.gsbitdz.downloadfilecsv I/Choreographer: Skipped 92 frames!  The application may be doing too much work on its main thread.
2020-12-21 21:40:16.394 10679-10706/com.gsbitdz.downloadfilecsv I/OpenGLRenderer: Davey! duration=1707ms; Flags=0, IntendedVsync=143238442663991, Vsync=143239975997263, OldestInputEvent=9223372036854775807, NewestInputEvent=0, HandleInputStart=143239981645120, AnimationStart=143239981761440, PerformTraversalsStart=143239982286150, DrawStart=143239988279900, SyncQueued=143239990141830, SyncStart=143240089030570, IssueDrawCommandsStart=143240089226000, SwapBuffers=143240092769820, FrameCompleted=143240248807880, DequeueBufferDuration=8247000, QueueBufferDuration=57494000, 
2020-12-21 21:40:21.830 10679-10706/com.gsbitdz.downloadfilecsv D/EGL_emulation: eglMakeCurrent: 0xe191a120: ver 3 0 (tinfo 0xe190f3a0)
2020-12-21 21:40:34.810 10679-10679/com.gsbitdz.downloadfilecsv W/System.err: java.io.FileNotFoundException: /storage/emulated/0/Download/amor.txt: open failed: EACCES (Permission denied)
2020-12-21 21:40:34.811 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at libcore.io.IoBridge.open(IoBridge.java:496)
2020-12-21 21:40:34.811 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at java.io.FileInputStream.<init>(FileInputStream.java:159)
2020-12-21 21:40:34.811 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at java.io.FileReader.<init>(FileReader.java:72)
2020-12-21 21:40:34.811 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at com.gsbitdz.downloadfilecsv.MainActivity.readText(MainActivity.java:57)
2020-12-21 21:40:34.811 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at com.gsbitdz.downloadfilecsv.MainActivity.onActivityResult(MainActivity.java:86)
2020-12-21 21:40:34.811 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at android.app.Activity.dispatchActivityResult(Activity.java:8110)
2020-12-21 21:40:34.811 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at android.app.ActivityThread.deliverResults(ActivityThread.java:4838)
2020-12-21 21:40:34.812 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at android.app.ActivityThread.handleSendResult(ActivityThread.java:4886)
2020-12-21 21:40:34.812 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:51)
2020-12-21 21:40:34.812 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
2020-12-21 21:40:34.812 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
2020-12-21 21:40:34.812 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
2020-12-21 21:40:34.812 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:107)
2020-12-21 21:40:34.812 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at android.os.Looper.loop(Looper.java:214)
2020-12-21 21:40:34.813 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:7356)
2020-12-21 21:40:34.813 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at java.lang.reflect.Method.invoke(Native Method)
2020-12-21 21:40:34.813 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
2020-12-21 21:40:34.813 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
2020-12-21 21:40:34.813 10679-10679/com.gsbitdz.downloadfilecsv W/System.err: Caused by: android.system.ErrnoException: open failed: EACCES (Permission denied)
2020-12-21 21:40:34.813 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at libcore.io.Linux.open(Native Method)
2020-12-21 21:40:34.814 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at libcore.io.ForwardingOs.open(ForwardingOs.java:167)
2020-12-21 21:40:34.814 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at libcore.io.BlockGuardOs.open(BlockGuardOs.java:252)
2020-12-21 21:40:34.814 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at libcore.io.ForwardingOs.open(ForwardingOs.java:167)
2020-12-21 21:40:34.814 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at android.app.ActivityThread$AndroidOs.open(ActivityThread.java:7255)
2020-12-21 21:40:34.814 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:     at libcore.io.IoBridge.open(IoBridge.java:482)
2020-12-21 21:40:34.814 10679-10679/com.gsbitdz.downloadfilecsv W/System.err:   ... 17 more
2020-12-21 21:40:35.473 10679-10706/com.gsbitdz.downloadfilecsv D/EGL_emulation: eglMakeCurrent: 0xe191a120: ver 3 0 (tinfo 0xe190f3a0)
2020-12-21 21:40:35.892 10679-10706/com.gsbitdz.downloadfilecsv D/EGL_emulation: eglMakeCurrent: 0xe191a120: ver 3 0 (tinfo 0xe190f3a0)
2020-12-21 21:40:35.964 10679-10706/com.gsbitdz.downloadfilecsv I/OpenGLRenderer: Davey! duration=1123ms; Flags=1, IntendedVsync=143258693907527, Vsync=143258760574191, OldestInputEvent=9223372036854775807, NewestInputEvent=0, HandleInputStart=143258765046080, AnimationStart=143258765134600, PerformTraversalsStart=143258765205160, DrawStart=143259742451060, SyncQueued=143259746669690, SyncStart=143259748996890, IssueDrawCommandsStart=143259749309920, SwapBuffers=143259752592880, FrameCompleted=143259819367860, DequeueBufferDuration=5693000, QueueBufferDuration=936000, 
2020-12-21 21:40:36.191 10679-10706/com.gsbitdz.downloadfilecsv D/EGL_emulation: eglMakeCurrent: 0xe191a120: ver 3 0 (tinfo 0xe190f3a0)

Answer 1

任何可能的解决方案将不再适用于较新的 Android 版本。有关一些提示，请参阅 [https://stackoverflow.com/questions/2902689/how-can-i-read-a-text-file-from-the-sd-card-in-android/]。请注意，从 Android 11 开始，Google 引入了非常严格的访问规则；特别是，任何应用程序都不得尝试访问其私有目录之外的文本或数据库文件。