我正在尝试通过单击按钮启动活动
- 当我单击按钮启动活动时，我得到
null pointer exception 因为我没有将任何价值从一项活动传递到另一项活动
空指针异常是如何发生的
- 如何解决这个问题
过滤器.java
public class Filters extends Activity implements OnSeekBarChangeListener{
// declare text objects variables
private SeekBar PRICEbar,DISTANCEbar, RATINGbar;
private TextView PRICEtextProgress,DISTANCEtextProgress, RATINGtextProgress;
Button back;
Button Done;
private RadioGroup rdg;
private RadioButton indian;
private RadioButton thai;
private RadioButton chinese;
private String selectedType="";
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// load the layout
setContentView(R.layout.filters);
/** Finding all the views in this Activity. */
PRICEbar = (SeekBar)findViewById(R.id.PRICEseekBarID); // make seekbar object
DISTANCEbar = (SeekBar)findViewById(R.id.DISTANCEseekBarID); // make seekbar object
RATINGbar = (SeekBar)findViewById(R.id.RATINGseekBarID); // make seekbar object
Done=(Button) findViewById(R.id.SEARCH_BUTTON_ID);
rdg = (RadioGroup) findViewById(R.id.radioGroup1);
indian = (RadioButton) findViewById(R.id.IndianRG_ID);
thai = (RadioButton) findViewById(R.id.ThaiRG_ID);
chinese = (RadioButton) findViewById(R.id.ChineseRG_ID);
rdg.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(RadioGroup radioGroup, int i) {
if(i==R.id.BreakfastRG_ID){
selectedType = indian.getText().toString();
}else if(i==R.id.LunchRG_ID){
selectedType = thai.getText().toString();
}else{
selectedType = chinese.getText().toString();
}
}
});
back=(Button) findViewById(R.id.TopNavigationBarFilterBackButton);
back.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
finish();
}
});
PRICEbar.setOnSeekBarChangeListener(this);
PRICEbar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
// TODO Auto-generated method stub
PRICEtextProgress = (TextView)findViewById(R.id.PRICEtextViewProgressID);
PRICEtextProgress.setText("Price:: Rs "+progress);
seekBar.setMax(100);
}
});
////////////////////////////////////////////////////////
DISTANCEbar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
// TODO Auto-generated method stub
DISTANCEtextProgress = (TextView)findViewById(R.id.DISTANCEtextViewProgressID);
DISTANCEtextProgress.setText("Distance:: "+progress);
seekBar.setMax(25);
}
});
////////////////////////////////////////////////////////
RATINGbar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
// TODO Auto-generated method stub
RATINGtextProgress = (TextView)findViewById(R.id.RATINGtextViewProgressID);
RATINGtextProgress.setText("Rating:: "+progress);
seekBar.setMax(5);
RatingBar ratingBar = (RatingBar)findViewById(R.id.RATINGfinalvalueratingID);
ratingBar.setRating(5);
ratingBar.setFocusable(false);
RatingBar ratingBar1 = (RatingBar)findViewById(R.id.RATINGinitialvalueratingID);
ratingBar1.setRating(0);
ratingBar.setFocusable(false);
}
});
Done.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent DoneIntent=new Intent(Filters.this,AndroidTabRestaurantDescFilterListView.class);
DoneIntent.putExtra("REST1",selectedType);
DoneIntent.putExtra("PriceBar", PRICEbar.getProgress());
DoneIntent.putExtra("DistanceBar", DISTANCEbar.getProgress());
DoneIntent.putExtra("RatingBar", RATINGbar.getProgress());
startActivity(DoneIntent);
}
});
}
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
if (seekBar == PRICEbar)
PRICEtextProgress.setText("Price:: Rs "+progress);
else if (seekBar == DISTANCEbar)
DISTANCEtextProgress.setText("Distance:: "+progress);
else if (seekBar == RATINGbar)
RATINGtextProgress.setText("Rating:: "+progress);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
}
AndroidTabRestaurantDescListView.java
public class AndroidTabRestaurantDescListView extends TabActivity {
// TabSpec Names
private static final String INBOX_SPEC = "Rating";
private static final String OUTBOX_SPEC = "Price";
private static final String PROFILE_SPEC = "Distance";
Button Photos;
Button Filter;
Button Search;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Photos=(Button) findViewById(R.id.PhotoButton);
Filter=(Button) findViewById(R.id.FilterButton);
Search=(Button) findViewById(R.id.SearchBottomBarID);
TabHost tabHost = getTabHost();
// Inbox Tab
TabSpec inboxSpec = tabHost.newTabSpec(INBOX_SPEC);
Intent inboxIntent = new Intent(this, MainActivity.class);
inboxSpec.setIndicator(INBOX_SPEC);
// Tab Content
inboxSpec.setContent(inboxIntent);
// Outbox Tab
TabSpec PriceSpec = tabHost.newTabSpec(OUTBOX_SPEC);
Intent PriceIntent = new Intent(this, PriceDescriptionActivity.class);
PriceSpec .setIndicator(OUTBOX_SPEC);
PriceSpec.setContent(PriceIntent);
// Profile Tab
TabSpec DistanceSpec = tabHost.newTabSpec(PROFILE_SPEC);
Intent DistanceIntent = new Intent(this, DistanceDiscriptionActivity.class);
DistanceSpec .setIndicator(PROFILE_SPEC);
DistanceSpec.setContent(DistanceIntent);
// Adding all TabSpec to TabHost
tabHost.addTab(inboxSpec);
tabHost.addTab(PriceSpec);
tabHost.addTab(DistanceSpec);
//Set the current value tab to default first tab
tabHost.setCurrentTab(0);
//Setting custom height for the tabs
final int height = 45;
tabHost.getTabWidget().getChildAt(0).getLayoutParams().height = height;
tabHost.getTabWidget().getChildAt(1).getLayoutParams().height = height;
tabHost.getTabWidget().getChildAt(2).getLayoutParams().height = height;
Photos.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
Intent PhotoIntent=new Intent(AndroidTabRestaurantDescListView.this,AndroidTabRestaurantDescImageListView.class);
startActivity(PhotoIntent);
}
});
Filter.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent FilterIntent=new Intent(AndroidTabRestaurantDescListView.this,Filters.class);
startActivity(FilterIntent);
}
});
Search.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent FilterIntent=new Intent(AndroidTabRestaurantDescListView.this,SearchPage.class);
startActivity(FilterIntent);
}
});
}
}
日志
10-21 14:49:54.117: D/AndroidRuntime(513): Shutting down VM
10-21 14:49:54.117: W/dalvikvm(513): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
10-21 14:49:54.127: E/AndroidRuntime(513): FATAL EXCEPTION: main
10-21 14:49:54.127: E/AndroidRuntime(513): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.androidbegin.jsonparsetutorial/com.project.findmybuffet.Filters}: java.lang.NullPointerException
10-21 14:49:54.127: E/AndroidRuntime(513): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
10-21 14:49:54.127: E/AndroidRuntime(513): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
10-21 14:49:54.127: E/AndroidRuntime(513): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
10-21 14:49:54.127: E/AndroidRuntime(513): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
10-21 14:49:54.127: E/AndroidRuntime(513): at android.os.Handler.dispatchMessage(Handler.java:99)
10-21 14:49:54.127: E/AndroidRuntime(513): at android.os.Looper.loop(Looper.java:123)
10-21 14:49:54.127: E/AndroidRuntime(513): at android.app.ActivityThread.main(ActivityThread.java:4627)
10-21 14:49:54.127: E/AndroidRuntime(513): at java.lang.reflect.Method.invokeNative(Native Method)
10-21 14:49:54.127: E/AndroidRuntime(513): at java.lang.reflect.Method.invoke(Method.java:521)
10-21 14:49:54.127: E/AndroidRuntime(513): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
10-21 14:49:54.127: E/AndroidRuntime(513): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
10-21 14:49:54.127: E/AndroidRuntime(513): at dalvik.system.NativeStart.main(Native Method)
10-21 14:49:54.127: E/AndroidRuntime(513): Caused by: java.lang.NullPointerException
10-21 14:49:54.127: E/AndroidRuntime(513): at com.project.findmybuffet.Filters.onCreate(Filters.java:179)
10-21 14:49:54.127: E/AndroidRuntime(513): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-21 14:49:54.127: E/AndroidRuntime(513): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
10-21 14:49:54.127: E/AndroidRuntime(513): ... 11 more
编辑
public class Filters extends Activity implements OnSeekBarChangeListener{
// declare text objects variables
private SeekBar PRICEbar,DISTANCEbar, RATINGbar;
private TextView PRICEtextProgress,DISTANCEtextProgress, RATINGtextProgress;
Button back;
Button FILTER;
private RadioGroup rdg;
private RadioButton indian;
private RadioButton thai;
private RadioButton chinese;
private String selectedType="";
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// load the layout
setContentView(R.layout.filters);
/** Finding all the views in this Activity. */
PRICEbar = (SeekBar)findViewById(R.id.PRICEseekBarID); // make seekbar object
DISTANCEbar = (SeekBar)findViewById(R.id.DISTANCEseekBarID); // make seekbar object
RATINGbar = (SeekBar)findViewById(R.id.RATINGseekBarID); // make seekbar object
FILTER=(Button) findViewById(R.id.SEARCH_BUTTON_ID);
rdg = (RadioGroup) findViewById(R.id.radioGroup1);
indian = (RadioButton) findViewById(R.id.IndianRG_ID);
thai = (RadioButton) findViewById(R.id.ThaiRG_ID);
chinese = (RadioButton) findViewById(R.id.ChineseRG_ID);
back=(Button) findViewById(R.id.TopNavigationBarFilterBackButton);
back.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
finish();
}
});
PRICEbar.setOnSeekBarChangeListener(this);
PRICEbar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
// TODO Auto-generated method stub
PRICEtextProgress = (TextView)findViewById(R.id.PRICEtextViewProgressID);
PRICEtextProgress.setText("Price:: Rs "+progress);
seekBar.setMax(100);
}
});
////////////////////////////////////////////////////////
DISTANCEbar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
// TODO Auto-generated method stub
DISTANCEtextProgress = (TextView)findViewById(R.id.DISTANCEtextViewProgressID);
DISTANCEtextProgress.setText("Distance:: "+progress);
seekBar.setMax(25);
}
});
////////////////////////////////////////////////////////
RATINGbar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
// TODO Auto-generated method stub
RATINGtextProgress = (TextView)findViewById(R.id.RATINGtextViewProgressID);
RATINGtextProgress.setText("Rating:: "+progress);
seekBar.setMax(5);
RatingBar ratingBar = (RatingBar)findViewById(R.id.RATINGfinalvalueratingID);
ratingBar.setRating(5);
ratingBar.setFocusable(false);
RatingBar ratingBar1 = (RatingBar)findViewById(R.id.RATINGinitialvalueratingID);
ratingBar1.setRating(0);
ratingBar.setFocusable(false);
}
});
rdg.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(RadioGroup radioGroup, int i) {
if(i==R.id.BreakfastRG_ID){
selectedType = indian.getText().toString();
}else if(i==R.id.LunchRG_ID){
selectedType = thai.getText().toString();
}else{
selectedType = chinese.getText().toString();
}
}
});
FILTER.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent FilterIntent=new Intent(Filters.this,AndroidTabRestaurantDescSearchListView.class);
FilterIntent.putExtra("REST1",selectedType);
FilterIntent.putExtra("PriceBar", PRICEbar.getProgress());
FilterIntent.putExtra("DistanceBar", DISTANCEbar.getProgress());
FilterIntent.putExtra("RatingBar", RATINGbar.getProgress());
startActivity(FilterIntent);
}
});
}
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
if (seekBar == PRICEbar)
PRICEtextProgress.setText("Price:: Rs "+progress);
else if (seekBar == DISTANCEbar)
DISTANCEtextProgress.setText("Distance:: "+progress);
else if (seekBar == RATINGbar)
RATINGtextProgress.setText("Rating:: "+progress);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
}
放置此代码后出现错误
FILTER.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent FilterIntent=new Intent(Filters.this,AndroidTabRestaurantDescSearchListView.class);
FilterIntent.putExtra("REST1",selectedType);
FilterIntent.putExtra("PriceBar", PRICEbar.getProgress());
FilterIntent.putExtra("DistanceBar", DISTANCEbar.getProgress());
FilterIntent.putExtra("RatingBar", RATINGbar.getProgress());
startActivity(FilterIntent);
}
});
该代码用于启动新活动，因此它是必不可少的