我复制了一些代码并且它有效，但是当我尝试进行一些更改时会引发异常，但我不知道为什么，因为我不了解所有代码，也许有人可以帮助我：< / p>
public class MainActivity extends ListActivity {
private File currentDir;
private FileArrayAdapter adapter;
private String SearchString = "test";
List<Option>dir = new ArrayList<Option>();
List<Option>fls = new ArrayList<Option>();
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
currentDir = new File("/sdcard/Test");
fill(currentDir);
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
// TODO Auto-generated method stub
super.onListItemClick(l, v, position, id);
Log.d("TEST", adapter.getItem(position).getPath());//aktuellen Pfad ins Syslog schreiben
Option o = adapter.getItem(position);
onFileClick(o);
}
private void onFileClick(Option o)
{
Log.d("TEST", o.getPath());//aktuellen Pfad ins Syslog schreiben
File file = new File(o.getPath());
Intent opdf = new Intent(Intent.ACTION_VIEW);
opdf.setDataAndType(Uri.fromFile(file), "application/pdf");
opdf.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);
startActivity(opdf);
}
public static String removeExtension(String s) {
String separator = System.getProperty("file.separator");
String filename;
// Remove the path upto the filename.
int lastSeparatorIndex = s.lastIndexOf(separator);
if (lastSeparatorIndex == -1) {
filename = s;
} else {
filename = s.substring(lastSeparatorIndex + 1);
}
// Remove the extension.
int extensionIndex = filename.lastIndexOf(".");
if (extensionIndex == -1)
return filename;
return filename.substring(0, extensionIndex);
}
private void fill(File f)
{
File[]dirs = f.listFiles();
try{
for(File ff: dirs)
{
if(ff.isDirectory()){
File r = new File (ff.getPath());
Log.d("TEST", ff.getPath());//aktuellen Pfad ins Syslog schreiben
fill2(r);
}
else
{
}
}
}catch(Exception e)
{
}
Collections.sort(dir);
Collections.sort(fls);
dir.addAll(fls);
adapter = new FileArrayAdapter(MainActivity.this,R.layout.activity_main,dir);
this.setListAdapter(adapter);
}
private void fill2(File f)
{
File[]dirs = f.listFiles();
try{
for(File ff: dirs)
{
if(ff.isDirectory()){
fill2(ff);
}
else{
String Name = (ff.getName().toLowerCase(Locale.GERMAN));
if (Name.contains(SearchString.toLowerCase(Locale.GERMAN))){
fls.add(new Option(removeExtension(ff.getName()),"",null));
}
}
}
}catch(Exception e)
{
}
}
}
public class FileArrayAdapter extends ArrayAdapter<Option>{
private Context c;
private int id;
private List<Option>items;
public FileArrayAdapter(Context context, int textViewResourceId,
List<Option> objects) {
super(context, textViewResourceId, objects);
c = context;
id = textViewResourceId;
items = objects;
}
public Option getItem(int i)
{
return items.get(i);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View v = convertView;
if (v == null) {
LayoutInflater vi = (LayoutInflater)c.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = vi.inflate(id, null);
}
final Option o = items.get(position);
if (o != null) {
TextView t1 = (TextView) v.findViewById(R.id.TextView01);
TextView t2 = (TextView) v.findViewById(R.id.TextView02);
if(t1!=null)
t1.setText(o.getName());
if(t2!=null)
t2.setText(o.getData());
//int drawableID = R.drawable.file_icon;
//t1.setCompoundDrawablesWithIntrinsicBounds(drawableID, 0,
// 0, 0);
t1.setEllipsize(null);
t1.setTextSize(54);
t1.setBackgroundColor(Color.LTGRAY);
t2.setBackgroundColor(Color.LTGRAY);
}
return v;
}
}
public class Option implements Comparable<Option>{
private String name;
private String data;
private String path;
public Option(String n,String d,String p)
{
name = n;
data = d;
path = p;
}
public String getName()
{
return name;
}
public String getData()
{
return data;
}
public String getPath()
{
return path;
}
@Override
public int compareTo(Option o) {
if(this.name != null)
return this.name.toLowerCase().compareTo(o.getName().toLowerCase());
else
throw new IllegalArgumentException();
}
}
E/AndroidRuntime(30173): FATAL EXCEPTION: main
E/AndroidRuntime(30173): java.lang.NullPointerException
E/AndroidRuntime(30173): at java.io.File.fixSlashes(File.java:185)
E/AndroidRuntime(30173): at java.io.File.<init>(File.java:134)
E/AndroidRuntime(30173): at com.example.test.MainActivity.onFileClick(MainActivity.java:47)
E/AndroidRuntime(30173): at com.example.test.MainActivity.onListItemClick(MainActivity.java:41)
E/AndroidRuntime(30173): at android.app.ListActivity$2.onItemClick(ListActivity.java:319)
E/AndroidRuntime(30173): at android.widget.AdapterView.performItemClick(AdapterView.java:297)
E/AndroidRuntime(30173): at android.widget.AbsListView.performItemClick(AbsListView.java:1100)
E/AndroidRuntime(30173): at android.widget.AbsListView$PerformClick.run(AbsListView.java:2754)
E/AndroidRuntime(30173): at android.widget.AbsListView$1.run(AbsListView.java:3428)
E/AndroidRuntime(30173): at android.os.Handler.handleCallback(Handler.java:725)
E/AndroidRuntime(30173): at android.os.Handler.dispatchMessage(Handler.java:92)
E/AndroidRuntime(30173): at android.os.Looper.loop(Looper.java:152)
E/AndroidRuntime(30173): at android.app.ActivityThread.main(ActivityThread.java:5132)
E/AndroidRuntime(30173): at java.lang.reflect.Method.invokeNative(NativeMethod)
E/AndroidRuntime(30173): at java.lang.reflect.Method.invoke(Method.java:511)
E/AndroidRuntime(30173): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
E/AndroidRuntime(30173): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
E/AndroidRuntime(30173): at dalvik.system.NativeStart.main(Native Method)
W/ActivityManager( 2112): Force finishing activity com.example.test/.MainActivity
答案 0 :(得分：0)
我认为来自您的对象“选项”的“路径”是正确的。
此行导致崩溃：
File file = new File(o.getPath());
关于你的方法“onFileClick”。
尝试打印o.getPath（）以查看他的值是什么，但我认为他可能是null。
答案 1 :(得分：0)
在 MainActivity 的 fill2 方法中，您正在创建一个带有空路径的Option对象：
fls.add(new Option(removeExtension(ff.getName()),"",null));
然后你正在打电话：
File file = new File(o.getPath());
抛出NullPointerException。
将以上行更改为：
fls.add(new Option(removeExtension(ff.getName()),"",ff.getPath()));