前言：
Android不支持pdf的在线预览，网上有多种预览pdf的实现方式，点此查看总结
这里实现一种先下载pdf文件到本地，再将文件转成图片显示的的操作
一个工具类：
代码语言：javascript复制import android.app.Application;
import android.arch.lifecycle.AndroidViewModel;
import android.arch.lifecycle.LiveData;
import android.arch.lifecycle.MutableLiveData;
import android.graphics.Bitmap;
import android.graphics.pdf.PdfRenderer;
import android.os.ParcelFileDescriptor;
import android.support.annotation.WorkerThread;
import android.util.Log;
import android.widget.ImageView;
import java.io.File;
import java.io.IOException;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import info.ecloud.core.util.ToastUtils;
import info.ecloud.merchant.app.BaseObserve;
import io.reactivex.Observable;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.schedulers.Schedulers;
public class PdfRendererBasicViewModel extends AndroidViewModel {
private static final String TAG = "PdfRendererBasic";
/**
* The filename of the PDF.
*/
private static final String FILENAME = "sample.pdf";
private final MutableLiveData<PageInfo> mPageInfo = new MutableLiveData<>();
private final MutableLiveData<Bitmap> mPageBitmap = new MutableLiveData<>();
private final MutableLiveData<Boolean> mPreviousEnabled = new MutableLiveData<>();
private final MutableLiveData<Boolean> mNextEnabled = new MutableLiveData<>();
private final Executor mExecutor;
private ParcelFileDescriptor mFileDescriptor;
private PdfRenderer mPdfRenderer;
private PdfRenderer.Page mCurrentPage;
private boolean mCleared;
public File pdfFile ;
public ImageView pdfView ;
@SuppressWarnings("unused")
public PdfRendererBasicViewModel(Application application , File pdfFile , ImageView pdfView) {
this(application, false);
this.pdfFile = pdfFile;
this.pdfView = pdfView;
}
PdfRendererBasicViewModel(Application application, boolean useInstantExecutor) {
super(application);
if (useInstantExecutor) {
mExecutor = Runnable::run;
} else {
mExecutor = Executors.newSingleThreadExecutor();
}
mExecutor.execute(() -> {
try {
openPdfRenderer();
showPage(0);
if (mCleared) {
closePdfRenderer();
}
} catch (IOException e) {
Log.e(TAG, "Failed to open PdfRenderer", e);
}
});
}
@Override
protected void onCleared() {
super.onCleared();
mExecutor.execute(() -> {
try {
closePdfRenderer();
mCleared = true;
} catch (IOException e) {
Log.i(TAG, "Failed to close PdfRenderer", e);
}
});
}
public LiveData<PageInfo> getPageInfo() {
return mPageInfo;
}
public LiveData<Bitmap> getPageBitmap() {
Log.i("xqxinfo","bitmap==>" (mPageBitmap==null));
return mPageBitmap;
}
public LiveData<Boolean> getPreviousEnabled() {
return mPreviousEnabled;
}
public LiveData<Boolean> getNextEnabled() {
return mNextEnabled;
}
void showPrevious() {
if (mPdfRenderer == null || mCurrentPage == null) {
return;
}
final int index = mCurrentPage.getIndex();
if (index > 0) {
mExecutor.execute(() -> showPage(index - 1));
}
}
public void showNext() {
if (mPdfRenderer == null || mCurrentPage == null) {
return;
}
final int index = mCurrentPage.getIndex();
if (index 1 < mPdfRenderer.getPageCount()) {
mExecutor.execute(() -> showPage(index 1));
}
}
public void showLast() {
if (mPdfRenderer == null || mCurrentPage == null) {
return;
}
final int index = mCurrentPage.getIndex();
if (index - 1 >=0) {
mExecutor.execute(() -> showPage(index - 1));
}
}
@WorkerThread
private void openPdfRenderer() throws IOException {
final File file = pdfFile;
if (!file.exists()) {
ToastUtils.showLong("文件预览失败");
return;
}
Log.i("xqxinfo","file->" file.getAbsolutePath());
mFileDescriptor = ParcelFileDescriptor.open(file, ParcelFileDescriptor.MODE_READ_ONLY);
if (mFileDescriptor != null) {
mPdfRenderer = new PdfRenderer(mFileDescriptor);
}
}
@WorkerThread
private void closePdfRenderer() throws IOException {
if (mCurrentPage != null) {
mCurrentPage.close();
}
if (mPdfRenderer != null) {
mPdfRenderer.close();
}
if (mFileDescriptor != null) {
mFileDescriptor.close();
}
}
@WorkerThread
private void showPage(int index) {
// Make sure to close the current page before opening another one.
if (null != mCurrentPage) {
mCurrentPage.close();
}
// Use `openPage` to open a specific page in PDF.
mCurrentPage = mPdfRenderer.openPage(index);
Bitmap bitmap = Bitmap.createBitmap(mCurrentPage.getWidth(), mCurrentPage.getHeight(),
Bitmap.Config.ARGB_8888);
// Here, we render the page onto the Bitmap.
// To render a portion of the page, use the second and third parameter. Pass nulls to get
// the default result.
// Pass either RENDER_MODE_FOR_DISPLAY or RENDER_MODE_FOR_PRINT for the last parameter.
mCurrentPage.render(bitmap, null, null, PdfRenderer.Page.RENDER_MODE_FOR_PRINT);
mPageBitmap.postValue(bitmap);
Observable.timer(10, TimeUnit.MILLISECONDS).subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new BaseObserve<Long>() {
@Override
public void onNext(Long aLong) {
pdfView.setImageBitmap(bitmap);
}
});
final int count = mPdfRenderer.getPageCount();
mPageInfo.postValue(new PageInfo(index, count));
mPreviousEnabled.postValue(index > 0);
mNextEnabled.postValue(index 1 < count);
}
static class PageInfo {
final int index;
final int count;
PageInfo(int index, int count) {
this.index = index;
this.count = count;
}
}
}使用方法：
代码语言：javascript复制public PdfRendererBasicViewModel(Application application , File pdfFile , ImageView pdfView) 注意，因为是图片方式显示，依赖于一个ImageView , 每次只显示pdf一页的数据预览，额外提供上一页、下一页的方法使用
这里只提供基本使用，可以自行拓展功能，不限于图片缩放，多页展示等
