我正在开发一个Android应用程序，该应用程序需要从手机浏览pdf，然后将其内容存储到String中。我有以下代码：
//src= location of the pdf file obtained from while browsing pdf from the phone (eg:"/sdcard/bluetooth/My_pdf.pdf")
public void convertPDFToText(String src) {
try {
//create pdf reader
PdfReader pr = new PdfReader(src);
//get the number of pages in the document
int pNum = pr.getNumberOfPages();
//extract text from each page and write it to the output text file
for (int page = 1; page <= pNum; page++) {
//text is the required String (initialized as "" )
text = text + PdfTextExtractor.getTextFromPage(pr, page);
}
} catch (Exception e) {
e.printStackTrace();
}
}
当我在java文件中单独运行此代码时，它运行得很好（根据系统中pdf的位置更改src输入），但是当我在android studio中运行相同的代码时，它给了我一个例外：
java.io.IOException: /sdcard/bluetooth/My_pdf.pdf not found as file or resource.
at com.itextpdf.text.io.RandomAccessSourceFactory.createByReadingToMemory(RandomAccessSourceFactory.java:263)
at com.itextpdf.text.io.RandomAccessSourceFactory.createBestSource(RandomAccessSourceFactory.java:173)
at com.itextpdf.text.pdf.PdfReader.<init>(PdfReader.java:223)
at com.itextpdf.text.pdf.PdfReader.<init>(PdfReader.java:207)
at com.itextpdf.text.pdf.PdfReader.<init>(PdfReader.java:197)
at com.example.prachisingh.summer.DisplayActivity.convertPDFToText(DisplayActivity.java:112)
at com.example.prachisingh.summer.DisplayActivity.onCreate(DisplayActivity.java:70)
at android.app.Activity.performCreate(Activity.java:6259)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1130)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2379)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2490)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1354)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5443)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) resource.I need help figuring out the cause of this error.
这是我的AndroidMAnifest.xml文件：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.Computer.app_name">
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity
android:name=".MainActivity"
android:label="@string/app_name"
android:theme="@style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".DisplayActivity" >
</activity>
<meta-data
android:name="com.google.android.gms.version"
android:value="@integer/google_play_services_version" />
</application>
添加权限：
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
到您的AndroidManifest.xml。
另外，如果您的目标SDK为23或更高版本，则您必须在应用运行时请求此权限。更多信息在这里
示例实现可能如下所示：
创建帮助程序类以请求权限
public class PermissionChecker {
private final Activity activity;
private final View layout;
private final int requestCode;
private final String permission;
private final String description;
public PermissionChecker(@NonNull Activity activity, @NonNull View layout,
int requestCode,
@NonNull String permission,
@NonNull String description) {
this.activity = activity;
this.layout = layout;
this.requestCode = requestCode;
this.permission = permission;
this.description = description;
}
public void requestPermission() {
if (ActivityCompat.shouldShowRequestPermissionRationale(activity, permission)) {
// Provide an additional rationale to the user if the permission was not granted
// and the user would benefit from additional context for the use of the permission.
// Display a SnackBar with a button to request the missing permission.
Snackbar.make(layout, description, Snackbar.LENGTH_INDEFINITE).setAction("OK", new View.OnClickListener() {
@Override
public void onClick(View view) {
requestPermission(activity, permission, requestCode);
}
}).show();
} else {
// No explanation needed, we can request the permission.
requestPermission(activity, permission, requestCode);
}
}
public boolean checkPermission() {
return ContextCompat.checkSelfPermission(activity, permission) == PackageManager.PERMISSION_GRANTED;
}
public boolean onRequestPermissionsResult(int requestCode, int[] grantResults) {
return requestCode == this.requestCode
&& ((grantResults.length > 0)
&& (grantResults[0] == PackageManager.PERMISSION_GRANTED));
}
private void requestPermission(Activity activityContext, String permission, int requestCode) {
ActivityCompat.requestPermissions(activityContext, new String[] { permission }, requestCode);
}
}
您的活动应实现OnRequestPermissionsResultCallback
实现ActivityCompat.OnRequestPermissionsResultCallback
用于外部存储权限的Init PermissionChecker。
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// ...
View rootView = getWindow().getDecorView().getRootView();
readExternalStoragePermissionChecker = new PermissionChecker(this, rootView,
PERMISSION_REQUEST_READ_EXTERNAL_STORAGE,
Manifest.permission.READ_EXTERNAL_STORAGE,
"Read external storage access is required to read pdfs from sdcard."
);
if (readExternalStoragePermissionChecker.checkPermission()) {
convertPDFToText(path);
}
else {
readExternalStoragePermissionChecker.requestPermission();
}
// ...
}
在您的Activity中覆盖onRequestPermissionsResult方法。
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
if (readExternalStoragePermissionChecker.onRequestPermissionsResult(requestCode, grantResults)) {
convertPDFToText(path);
}
}
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