应用程序从 sdcard 中列出活动中的 Pdf

Question

I am developing an app in android which requires a list activity to show all pdfs from sdcard..i found the below code and used it but it is not working my app is unfortunately closing.. can anyone tell me whats the error.

MainActivity.java

package com.example.vinita.listallpdfs;

import android.app.ListActivity;
import android.os.Bundle;
import android.os.Environment;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ArrayAdapter;
import java.io.File;
import java.io.FilenameFilter;
import java.util.ArrayList;
import java.util.Arrays;

import static com.example.vinita.listallpdfs.R.layout.activity_main;


public class MainActivity extends ListActivity {
    ArrayAdapter adapter;
    int clickCounter=0;
    ArrayList listItems=new ArrayList();
    private File[] imagelist;
    String[] pdflist;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(activity_main);
        File images = Environment.getExternalStorageDirectory();
        //ListView list=(ListView)findViewById(R.id.list);
        imagelist = images.listFiles(new FilenameFilter() {
            @Override
            public boolean accept(File dir, String name) {
                return ((name.endsWith(".pdf")));
            }
        });
        pdflist = new String[imagelist.length];
        for (int i = 0; i < imagelist.length; i++) {
            pdflist[i] = imagelist[i].getName();
        }
        Arrays.sort(imagelist);
        Arrays.sort(pdflist);
        this.setListAdapter(new ArrayAdapter(this, android.R.layout.simple_list_item_1, pdflist));
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity"
    android:background="#ff3db0ff"
    android:orientation="vertical">


    <ListView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@android:id/list"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:scrollbars="vertical"/>
</RelativeLayout>

Answer 1

Add this permission to your manifest file

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

hope it helps :D