應用程序從 sdcard 中列出活動中的 Pdf

Question

我正在android中開發一個應用程序，它需要一個列表活動來顯示sdcard中的所有pdf..我找到了下面的代碼並使用了它但它不起作用我的應用程序不幸關閉..誰能告訴我錯誤是什么。

主活動.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);
    }
}

活動_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

將此權限添加到您的清單文件

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

希望它有幫助：D