I want to run the application in ma Galaxy S2 but I found this error.I post the logcat.please tell me what's the problem? and how to resolve it ? thanks
05-07 11:23:38.820: D/AndroidRuntime(8900): Shutting down VM
05-07 11:23:38.820: W/dalvikvm(8900): threadid=1: thread exiting with uncaught exception (group=0x40c3f1f8)
05-07 11:23:38.820: E/AndroidRuntime(8900): FATAL EXCEPTION: main
05-07 11:23:38.820: E/AndroidRuntime(8900): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.aaaaa/com.example.aaaaa.MainActivity}: java.lang.NullPointerException
05-07 11:23:38.820: E/AndroidRuntime(8900): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1892)
05-07 11:23:38.820: E/AndroidRuntime(8900): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1993)
05-07 11:23:38.820: E/AndroidRuntime(8900): at android.app.ActivityThread.access$600(ActivityThread.java:127)
05-07 11:23:38.820: E/AndroidRuntime(8900): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1159)
05-07 11:23:38.820: E/AndroidRuntime(8900): at android.os.Handler.dispatchMessage(Handler.java:99)
05-07 11:23:38.820: E/AndroidRuntime(8900): at android.os.Looper.loop(Looper.java:137)
05-07 11:23:38.820: E/AndroidRuntime(8900): at android.app.ActivityThread.main(ActivityThread.java:4507)
05-07 11:23:38.820: E/AndroidRuntime(8900): at java.lang.reflect.Method.invokeNative(Native Method)
05-07 11:23:38.820: E/AndroidRuntime(8900): at java.lang.reflect.Method.invoke(Method.java:511)
05-07 11:23:38.820: E/AndroidRuntime(8900): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
05-07 11:23:38.820: E/AndroidRuntime(8900): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
05-07 11:23:38.820: E/AndroidRuntime(8900): at dalvik.system.NativeStart.main(Native Method)
05-07 11:23:38.820: E/AndroidRuntime(8900): Caused by: java.lang.NullPointerException
05-07 11:23:38.820: E/AndroidRuntime(8900): at android.content.ContextWrapper.getResources(ContextWrapper.java:81)
05-07 11:23:38.820: E/AndroidRuntime(8900): at android.view.View.<init>(View.java:2721)
05-07 11:23:38.820: E/AndroidRuntime(8900): at android.view.View.<init>(View.java:2769)
05-07 11:23:38.820: E/AndroidRuntime(8900): at android.widget.TextView.<init>(TextView.java:573)
05-07 11:23:38.820: E/AndroidRuntime(8900): at android.widget.TextView.<init>(TextView.java:566)
05-07 11:23:38.820: E/AndroidRuntime(8900): at android.widget.TextView.<init>(TextView.java:561)
05-07 11:23:38.820: E/AndroidRuntime(8900): at com.example.aaaaa.MainActivity.<init>(MainActivity.java:28)
05-07 11:23:38.820: E/AndroidRuntime(8900): at java.lang.Class.newInstanceImpl(Native Method)
05-07 11:23:38.820: E/AndroidRuntime(8900): at java.lang.Class.newInstance(Class.java:1319)
05-07 11:23:38.820: E/AndroidRuntime(8900): at android.app.Instrumentation.newActivity(Instrumentation.java:1026)
05-07 11:23:38.820: E/AndroidRuntime(8900): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1883)
05-07 11:23:38.820: E/AndroidRuntime(8900): ... 11 more
这是MainActivity.java，我认为错误是出在 TextView view = new TextView(this); 因为我在MainActivity中没有TextView，但我想在另一个类（setting.java）中从textview中提取数据。
import java.util.ArrayList;
import java.util.List;
import android.content.Intent;
import android.database.Cursor;
import android.graphics.drawable.Drawable;
import android.net.Uri;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import com.google.android.maps.GeoPoint;
import com.google.android.maps.ItemizedOverlay;
import com.google.android.maps.MapActivity;
import com.google.android.maps.MapController;
import com.google.android.maps.MapView;
import com.google.android.maps.OverlayItem;
public class MainActivity extends MapActivity {
String num;
TextView view = new TextView(this);
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Bundle extra = getIntent().getExtras();
num = extra.getString("label");
final TextView view = new TextView(this);
Uri uriSMSURI = Uri.parse("content://sms/inbox");
Cursor cur = getContentResolver().query(uriSMSURI, null, null, null,null);
String sms = "";
while (cur.moveToNext()) {
String spn ="+21629188153";
String phNum =cur.getString(2);
if (spn.equals(phNum)){
sms +=cur.getString(12);
}
}
String a =sms.substring(0,10);
String b =sms.substring(11,21);
MapView maMap;
MapController monControler;
maMap = (MapView)findViewById(R.id.myGmap);
maMap.setBuiltInZoomControls(true);
GeoPoint point = new GeoPoint (microdegrees(Double.parseDouble(a)),microdegrees(Double.parseDouble(b)));
MonOverlay object = new MonOverlay(getResources().getDrawable(R.drawable.marker_voisinage_rouge));
object.addPoint(point);
maMap.getOverlays().add(object);
maMap.setSatellite(true);
monControler = maMap.getController();
monControler.setZoom(12);
monControler.setCenter(point);
Button monBouton = (Button)findViewById(R.id.envoie_sms);
monBouton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
View monBoutton = null;
// TODO Auto-generated method stub
Intent monIntent = new Intent(MainActivity.this,SendSms.class);
startActivity(monIntent);
}
} );
Button mnBouton = (Button)findViewById(R.id.setting);
mnBouton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
View monBoutton = null;
// TODO Auto-generated method stub
setContentView(R.layout.setting);
}
} );
Button myBouton = (Button)findViewById(R.id.aff);
myBouton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
View monBoutton = null;
// TODO Auto-generated method stub
view.setText(num);
setContentView(view);
}
} );
}
private int microdegrees (double value){
return (int)(value*1000000);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
@Override
protected boolean isRouteDisplayed() {
// TODO Auto-generated method stub
return false;
}
public class MonOverlay extends ItemizedOverlay<OverlayItem>{
List<GeoPoint> points = new ArrayList<GeoPoint>();
public MonOverlay(Drawable arg0) {
super(boundCenterBottom(arg0));
// TODO Auto-generated constructor stub
}
@Override
protected OverlayItem createItem(int i) {
GeoPoint point = points.get(i);
return new OverlayItem(point,"titre","description");
}
@Override
public int size() {
return points.size();
}
public void addPoint (GeoPoint point){
this.points.add(point);
populate();
}
}
}
这是 Setting.java，我想通过 s1 = num.getText().toString(); 到MainActivity.java
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class setting extends Activity {
Button sauvg;
EditText num;
String s1;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.setting);
sauvg = (Button)findViewById(R.id.ok);
num = (EditText)findViewById(R.id.editText1);
sauvg.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v)
{
Intent t = new Intent(setting.this, MainActivity.class);
s1 = num.getText().toString();
t.putExtra("label",s1);
startActivity(t);
// TODO Auto-generated method stub
}
});
}
}
错误在这里。
public class MainActivity extends MapActivity {
String num;
TextView view = new TextView(this); // <- HERE
你不能在那里创建一个视图，但你应该把创建的视图移到... ... onCreate 方法，像这样。
public class MainActivity extends MapActivity {...
String num;
TextView view;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
this.view = new TextView(this);
Bundle extra = getIntent().getExtras();
小心变量名：我看到你有两个叫 "view "的变量，这并不是一个错误（一个是本地变量，在 onCreate，另一个是实例变量）但很容易出错。
顺便说一下，你不能直接访问其他Activity中的TextView，如果你想在Activity之间共享数据，你应该使用Intents或Message&Handler。如果你想在活动之间共享数据，你应该使用Intents或者Message&Handler。
如果MainActivity是你的应用启动时启动的第一个活动，我想你的应用就会崩溃。出现这种情况是因为你在使用之前应该检查调用意图是否有额外的内容，比如这样。
Bundle extra = getIntent().getExtras();
if (extra != null) {
num = extra.getString("label");
}