问题描述
我想使用 AndroidPdfViewer 从外部存储 (Download/Pdfs/myfile.pdf) 加载 pdf 文件,但它显示空白屏幕而没有任何错误。我尝试了很多方法,但都行不通。
public class PdfViewActivity2 extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
File path = new File(Environment.getExternalStorageDirectory().getPath() + "/Download/Pdfs/myfile.pdf");
PDFView pdfView = findViewById(R.id.pdfView);
pdfView.fromFile(path).load();
我的“下载/Pdfs/myfile.pdf”中有一个 pdf 文件,我使用上面的代码加载文件,但它不起作用。 我已从设置中手动授予存储权限。 任何人都可以在我犯的错误的地方纠正我。
解决方法
首先,将库添加到您的 build.gradle 文件中
implementation 'com.github.barteksc:android-pdf-viewer:2.8.2'
要从存储打开 PDF 文件,请使用此代码。有一些评论解释了它的作用。
public class PdfViewActivity2 extends AppCompatActivity {
// Declare PDFView variable
private PDFView pdfView;
private final int PDF_SELECTION_CODE = 99;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Initialize it
pdfView = findViewById(R.id.pdfView);
// Select PDF from storage
// This code can be used in a button
Toast.makeText(this,"selectPDF",Toast.LENGTH_LONG).show();
Intent browseStorage = new Intent(Intent.ACTION_GET_CONTENT);
browseStorage.setType("application/pdf");
browseStorage.addCategory(Intent.CATEGORY_OPENABLE);
startActivityForResult(Intent.createChooser(browseStorage,"Select PDF"),PDF_SELECTION_CODE);
}
// Get the Uniform Resource Identifier (Uri) of your data,and receive it as a result.
// Then,use URI as the pdf source and pass it as a parameter inside this method fromUri(Uri uri)
@Override
protected void onActivityResult(int requestCode,int resultCode,@Nullable Intent data) {
super.onActivityResult(requestCode,resultCode,data);
if (requestCode == PDF_SELECTION_CODE && resultCode == Activity.RESULT_OK && data != null) {
Uri selectedPdfFromStorage = data.getData();
pdfView.fromUri(selectedPdfFromStorage).defaultPage(0).load();
}
}
}
,
在 Android 10 设备中,您的应用无法访问外部存储。
除非你添加
String
在清单文件的应用程序标签中。
,不要使用 fromFile() 使用 fromSource()。即,将 pathe 声明为 DocumentSource 而不是 File。
public class PdfViewActivity2 extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
DocumentSource path = new File(Environment.getExternalStorageDirectory().getPath() + "/Download/myfile.pdf");
PDFView pdfView = findViewById(R.id.pdfView);
pdfView.fromSource(path).load();
,
我已经测试了您的代码,它在 Android 10 设备上运行良好。您缺少以下内容:
1.在Android Manifest File中添加READ_EXTERNAL_STORAGE权限
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
并在应用程序内部标记中将 requestLegacyExternalStorage 添加为 true,以便能够访问 Android 10 及更高版本设备上的外部存储。
<application
android:requestLegacyExternalStorage="true"
2.验证设备上“/Download/Pdfs/myfile.pdf”路径下的pdf是否存在。
3.通过在运行时首先在 onCreate 方法中请求外部存储权限,使用以下代码更改您的活动:
public class PdfViewActivity2 extends AppCompatActivity {
private static final int READ_STORAGE_PERMISSION_REQUEST_CODE = 1000;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//check if Read External Storage permission was granded
boolean granded = checkPermissionForReadExtertalStorage();
if(!granded){
requestPermissionForReadExtertalStorage();
}
else {
readPdf();
}
}
public boolean checkPermissionForReadExtertalStorage() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
int result = checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE);
return result == PackageManager.PERMISSION_GRANTED;
}
return false;
}
public void requestPermissionForReadExtertalStorage() {
try {
ActivityCompat.requestPermissions(this,new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},READ_STORAGE_PERMISSION_REQUEST_CODE);
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
public void onRequestPermissionsResult(int requestCode,@NonNull String[] permissions,@NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode,permissions,grantResults);
switch (requestCode) {
case READ_STORAGE_PERMISSION_REQUEST_CODE: {
// If request is cancelled,the result arrays are empty.
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// permission was granted. Read Pdf from External Storage
readPdf();
} else {
// permission denied. Disable the functionality that depends on this permission.
}
}
}
}
private void readPdf(){
File path = new File(Environment.getExternalStorageDirectory().getPath() + "/Download/Pdfs/myfile.pdf");
PDFView pdfView = findViewById(R.id.pdfView);
pdfView.fromFile(path).load();
}
}