我试图用所有相关的答案解决这个谜题，但我似乎无法连接点。
我的MainActivity（下面的代码）中有4个选项卡可以正常工作，在每个选项卡中显示产品列表。
单击产品时，记录的ID将传递给ViewProduct Activity（下面的代码），其中id用于填充产品的详细信息，并再次通过bundle传递给4个片段以显示项目与该产品有关。
所有这些“List Loading”和“Passing”参数都运行正常，但ViewPager / SectionsAdaptor表现得很有趣......
在第一个tab1，tab3和tab4是好的，但tab2是空白的，然后当你“选择”到tab4并返回到tab1，tab1是空白等等。似乎页面/片段被加载两次这可能成为问题的原因。
因此，单独所有片段都能正常工作。为什么会这样？ 请帮忙！
注意：我遗漏了一些不相关的代码，例如设置TextViews等并用注释替换它，所以请注意注释并建议扩展哪个Activity
谢谢
这是我的MainActivity.java
public class MainActivity extends AppCompatActivity {
private SectionsPagerAdapter mSectionsPagerAdapter;
private AddUpdateProductOps productOps;
private ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
this.getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_ADJUST_RESIZE);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
Products tab1 = new Products();
return tab1;
case 1:
Sales tab2 = new Sales();
return tab2;
case 2:
Orders tab3 = new orders();
return tab3;
case 3:
Clients tab4 = new Clients();
return tab4;
default:
return null;
}
}
@Override
public int getCount() {
// Show 3 total pages.
return 4;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "Products";
case 1:
return "Sales";
case 2:
return "Orders";
case 3:
return "Clients";
}
return null;
}
}
**这是我的ViewProduct.jave **
public class ViewProduct extends AppCompatActivity {
private Button actionButton1;
private Product oldProduct;
private long productId;
private AddUpdateProductOps productOps;
private TextView EditTextNo;
private TextView EditTextOrigin, ..., ..., ..., ...;
private TextView tv_banner_txt;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.view_product);
final Context[] context = new Context[1];
productId = getIntent().getLongExtra(EXTRA_PRODUCT_ID,0);
if (productId < 1){
productId = Long.parseLong(getIntent().getStringExtra(EXTRA_PRODUCT_IDE));
}
oldProduct = new Product();
productOps = new AddUpdateProductOps(this);
>Some TextViews are set over here.....(not Included) - findViewById(....) - No >Problem
actionButton1.setText("EDIT");
tv_banner_txt.setText("VIEW THE PRODUCT");
initializeProduct(productId);
mSectionsPagerAdapter = new ViewProduct.SectionsPagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager,false);
GradientDrawable border = new GradientDrawable();
border.setStroke(7, 0xFF000000); //black border with full opacity'
border.setCornerRadius(10);
if(Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN) {
tabLayout.setBackgroundDrawable(border);
} else {
tabLayout.setBackground(border);
}
actionButton1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(final View v) {
context[0] = v.getContext();
Intent i = new Intent(ViewProduct.this, AddUpdateProduct.class);
i.putExtra(EXTRA_ADD_UPDATE, "Update");
i.putExtra(EXTRA_PRODUCT_ID, productId);
startActivity(i);
finish();
}
});
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(final View v) {
context[0] = v.getContext();
Intent i = new Intent(ViewProduct.this, AddUpdateEvf.class);
i.putExtra(EXTRA_ADD_UPDATE, "Add");
i.putExtra(EXTRA_PRODUCT_NO, oldProduct.getProductNo());
i.putExtra(EXTRA_PRODUCT_ID, productId);
startActivityForResult(i,12);
finish();
}
});
}
private void initializeProduct(long productId) {
oldProduct = productOps.getProduct(productId);
EditTextNo.setText(oldProduct.getProductNo());
EditTextOrigin.setText(oldProduct.getOrigin());
tv_cat.setText(oldProduct.getCat);
tv_Weight.setText(pldProduct.getWeight);
EditTextSize.setText(oldProduct.getSize());
EditTextVolume.setText(oldProduct.getVolume());
}
private SectionsPagerAdapter mSectionsPagerAdapter;
private ViewPager mViewPager;
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
Fragment tab1 = createCustomFragment1();
return tab1;
case 1:
Fragment tab2 = createCustomFragment2();
return tab2;
case 2:
Fragment tab3 = createCustomFragment3();
return tab3;
case 3:
Fragment tab4 = createCustomFragment4();
return tab4;
default:
return null;
}
}
@Override
public int getCount() {
// Show 3 total pages.
return 4;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "Sales";
case 1:
return "Oders";
case 2:
return "Suppliers";
case 3:
return "Actions";
}
return null;
}
}
public Fragment createCustomFragment1(){
final FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
final Sales salesFrg = new Sales();
ft.replace(R.id.container, salesFrg);
final Bundle bdl = new Bundle();
bdl.putString("productIde", String.valueOf(productId));
salesFrg.setArguments(bdl);
ft.commit();
return salesFrg;
}
> createCustomFragment2(),createCustomFragment3(),createCustomFragment4() >looks exactly like createCustomFragment1()
}