新手求教,報空指針異常:
package com.sweetstar86.day6hw;
import android.app.Activity;
import android.content.Intent;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import java.util.ArrayList;
public class GuideActivity extends Activity implements ViewPager.OnPageChangeListener {
private ViewPager viewPager;
private ArrayList<View> views = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_guide);
initView();
}
public void initView() {
views.add(getLayoutInflater().inflate(R.layout.layout_pre1, null));
views.add(getLayoutInflater().inflate(R.layout.layout_pre2, null));
viewPager.setOnPageChangeListener(this);
viewPager.setAdapter(new MyPageAdapter());
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
}
@Override
public void onPageScrollStateChanged(int state) {
if (state == views.size()) {
Intent mainIntent = new Intent(GuideActivity.this, MainActivity.class);
GuideActivity.this.startActivity(mainIntent);
GuideActivity.this.finish();
}
}
class MyPageAdapter extends PagerAdapter {
@Override
public int getCount() {
return views.size();
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
View v = views.get(position);
container.addView(v);
return v;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView(views.get(position));
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}
}
}
在viewPager.setOnPageChangeListener(this);和
initView();
處,報錯。
viewPager沒有初始化
需要加上
viewPager = (ViewPager)findViewById(R.id.xxxxxx);//viewpage的id找到對應的viewpage