在淘寶、網易雲音樂 等等APP應用中我們隨處可見小圓點與ViewPager的輪播組合 可見它的應用十分廣泛 那麼到底如何實現 現在讓我們一起來學習!
一 在佈局中寫出vp與圓點
<RelativeLayout
android:id="@+id/rl"
android:layout_width="match_parent"
android:layout_height="300dp">
<android.support.v4.view.ViewPager
android:id="@+id/vp"
android:layout_width="match_parent"
android:layout_height="300dp"
></android.support.v4.view.ViewPager>
<LinearLayout
android:id="@+id/ll"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_marginBottom="40dp"
android:gravity="center"
android:orientation="horizontal"></LinearLayout>
</RelativeLayout>
自定義接口的過程中我們需要兩張圖片 R.mipmap.gouwuzy_16 R.mipmap.gouwuzy_17一個選中的圖片 一個未選中
放入mipmap中 在調用接口時我們需要傳入4個參數上下文、我們佈局中的VP及LinerLayout、ViewPager中圖片個個
數。
public class ViewPagerIndicator implements ViewPager.OnPageChangeListener {
private Context context;
private ViewPager viewPager;
private LinearLayout dotLayout;
private int size;
private int img1 = R.mipmap.gouwuzy_16, img2 = R.mipmap.gouwuzy_17;
private int imgSize = 15;
private List<ImageView> dotViewLists = new ArrayList<>();
public ViewPagerIndicator(Context context, ViewPager viewPager, LinearLayout dotLayout, int size) {
this.context = context;
this.viewPager = viewPager;
this.dotLayout = dotLayout;
this.size = size;
for (int i = 0; i < size; i++) {
ImageView imageView = new ImageView(context);
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
//爲小圓點左右添加間距
params.leftMargin = 10;
params.rightMargin = 10;
//手動給小圓點一個大小
params.height = imgSize;
params.width = imgSize;
if (i == 0) {
imageView.setBackgroundResource(img1);
} else {
imageView.setBackgroundResource(img2);
}
//爲LinearLayout添加ImageView
dotLayout.addView(imageView, params);
dotViewLists.add(imageView);
}
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
for (int i = 0; i < size; i++) {
//選中的頁面改變小圓點爲選中狀態,反之爲未選中
if ((position % size) == i) {
((View) dotViewLists.get(i)).setBackgroundResource(img1);
} else {
((View) dotViewLists.get(i)).setBackgroundResource(img2);
}
}
}
@Override
public void onPageScrollStateChanged(int state) {
}
}
public class MainActivity extends AppCompatActivity {
private ViewPager vp;
private VPAdapter vpAdapter;
private LinearLayout ll;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
vp = (ViewPager) findViewById(R.id.vp);
vpAdapter = new VPAdapter(this);
vp.setAdapter(vpAdapter);
ll = (LinearLayout) findViewById(R.id.ll);
vp.setOnPageChangeListener(new ViewPagerIndicator(this, vp, ll, 3));
}
}
接口調用中的第四個參數是可變的 當我們從網站讀取數據時參數爲ViewPagerimg集合的長度