问题
public class AddActivity extends Activity implements OnClickListener{
String[] info = new String[11];
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.add_layout);
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
TextView keyString = (TextView)findViewById(R.id.keyString);
TextView site1 = (TextView)findViewById(R.id.site1);
TextView site2 = (TextView)findViewById(R.id.site2);
TextView site3 = (TextView)findViewById(R.id.site3);
ImageButton submit = (ImageButton)findViewById(R.id.submit);
ImageButton add1 = (ImageButton)findViewById(R.id.add1);
ImageButton add2 = (ImageButton)findViewById(R.id.add2);
ImageButton add3 = (ImageButton)findViewById(R.id.add3);
submit.setOnClickListener((OnClickListener) this);
add1.setOnClickListener((OnClickListener) this);
add2.setOnClickListener((OnClickListener) this);
add3.setOnClickListener((OnClickListener) this);
int id = v.getId();
switch(id){
case R.id.submit:{
submitEntry(info);
break;
}
case R.id.add1:{
add2.setVisibility(View.VISIBLE);
site2.setVisibility(View.VISIBLE);
break;
}
}
}
}
This is the code.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/key_string"
android:textAppearance="?android:attr/textAppearanceLarge" />
<TextView
android:id="@+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceSmall"
android:visibility="invisible" />
<EditText
android:id="@+id/keyString"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge" />
<TextView
android:id="@+id/textView4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceMedium"
android:visibility="invisible" />
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/site_string"
android:textAppearance="?android:attr/textAppearanceLarge" />
<TextView
android:id="@+id/textView6"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceSmall"
android:visibility="invisible" />
<ScrollView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<ImageButton
android:id="@+id/add1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_action_new" />
<EditText
android:id="@+id/site1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/url_hint"
android:textAppearance="?android:attr/textAppearanceLarge" />
</LinearLayout>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceSmall"
android:visibility="invisible" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<ImageButton
android:id="@+id/add2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_action_new"
android:visibility="invisible" />
<EditText
android:id="@+id/site2"
android:layout_width="match_parent"
android:layout_height="fill_parent"
android:text="@string/url_hint"
android:textAppearance="?android:attr/textAppearanceLarge"
android:visibility="invisible" />
</LinearLayout>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceSmall"
android:visibility="invisible" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<ImageButton
android:id="@+id/add3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_action_new"
android:visibility="invisible" />
<EditText
android:id="@+id/site3"
android:layout_width="match_parent"
android:layout_height="fill_parent"
android:text="@string/url_hint"
android:visibility="invisible"
android:textAppearance="?android:attr/textAppearanceLarge" />
</LinearLayout>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceSmall"
android:visibility="invisible" />
<Button
android:id="@+id/submit"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="@string/submit_buttom" />
</LinearLayout>
</ScrollView>
</LinearLayout>
And this is the XML. The add1, add2, add3 and submit ImageButtons are all in a ScrollView.
When I press the add1 ImageButton, I want the add2 and site2 ImageButtons to become visible but instead, it throws the following error.
Motion event has invalid pointer count 0; value must be between 1 and 16.
What am I doing wrong?
PS: All the findViewById() calls are in the onClick() method because a NullPointerExeption is thrown if I call them in the onCreate().
回答1:
Those findViewByIdcalls in onClickdon't make sense. Not sure why you are getting a null pointer exception calling them in onCreate.onClick is never called in this instance because nothing in the creation of the Activity is assigning the buttons to look at your onClick method; the buttons will default to having no listener assigned. It also doesn't look like a good idea to use the Activity as the onClickListener as well.
Your code should look something like this:
public class AddActivity extends Activity {
// https://source.android.com/source/code-style.html
// info -> mInfo; non-public, non-static field!
String[] mInfo = new String[11];
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.add_layout);
TextView keyString = (TextView)findViewById(R.id.keyString);
TextView site1 = (TextView)findViewById(R.id.site1);
TextView site2 = (TextView)findViewById(R.id.site2);
TextView site3 = (TextView)findViewById(R.id.site3);
Button submit = (Button)findViewById(R.id.submit);
ImageButton add1 = (ImageButton)findViewById(R.id.add1);
ImageButton add2 = (ImageButton)findViewById(R.id.add2);
ImageButton add3 = (ImageButton)findViewById(R.id.add3);
add1.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
add2.setVisibility(View.VISIBLE);
site2.setVisibility(View.VISIBLE);
}
});
submit.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
submitEntry(mInfo);
}
});
}
回答2:
The findViewById() calls and especially the setOnClickListener() calls should have been inside the onCreate(). With setOnClickListener() inside the onClick() i doubt the onClick was ever called.
We would need more logs to find the exact issue.
来源：https://stackoverflow.com/questions/28411401/motion-event-error-on-imagebutton-click