1.全部代码
3个fragment的代码：
public class BlankFragment extends Fragment {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@SuppressLint("ResourceAsColor")
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
TextView textView=new TextView(getActivity());
textView.setText("1111111111111111");
textView.setTextSize(50);
textView.setTextColor(Color.parseColor("#FFFFFF"));
textView.setBackgroundColor(R.color.colorAccent);
return textView;
}
}
public class BlankFragment2 extends Fragment {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@SuppressLint("ResourceAsColor")
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
TextView textView=new TextView(getActivity());
textView.setText("2222222222222222222222222");
textView.setBackgroundColor(R.color.colorPrimaryDark);
return textView;
}
}
public class BlankFragment3 extends Fragment {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@SuppressLint("ResourceAsColor")
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
TextView textView=new TextView(getActivity());
textView.setText("3333333333333333333333333333");
textView.setBackgroundColor(R.color.colorPrimary);
return textView;
}
}
xml代码：
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity">
<Button android:id="@+id/bt_1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginBottom="16dp" android:text="1" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toStartOf="@+id/bt2" app:layout_constraintStart_toStartOf="parent" />
<Button android:id="@+id/bt2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="2" app:layout_constraintBottom_toBottomOf="@+id/bt_1" app:layout_constraintEnd_toStartOf="@+id/bt3" app:layout_constraintStart_toEndOf="@+id/bt_1" app:layout_constraintTop_toTopOf="@+id/bt_1" />
<Button android:id="@+id/bt3" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="3" app:layout_constraintBottom_toBottomOf="@+id/bt2" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toEndOf="@+id/bt2" app:layout_constraintTop_toTopOf="@+id/bt2" />
<FrameLayout android:id="@+id/fl" android:layout_width="409dp" android:layout_height="665dp" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent">
</FrameLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
主界面代码：
public class Main2Activity extends AppCompatActivity implements View.OnClickListener {
private static final String TAG = "MainActivity";
private Button mBt1;
private Button mBt2;
private Button mBt3;
private FrameLayout mFl;
private BlankFragment blankFragment;
private BlankFragment2 blankFragment2;
private BlankFragment3 blankFragment3;
private FragmentTransaction mFragmentTransaction;
List<Fragment> list=new LinkedList<>();
private FragmentTransaction fragmentTransaction;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
//1.添加全部fragment，默认只显示1
blankFragment = new BlankFragment();
blankFragment2 = new BlankFragment2();
blankFragment3 = new BlankFragment3();
FragmentManager supportFragmentManager = getSupportFragmentManager();
mFragmentTransaction = supportFragmentManager.beginTransaction();
mFragmentTransaction
.add(R.id.fl, blankFragment, "blankFragment")
.add(R.id.fl, blankFragment2, "blankFragment2")
.add(R.id.fl, blankFragment3, "blankFragment3")
.hide(blankFragment2)
.hide(blankFragment3).commit();
}
private void initView() {
mBt1 = (Button) findViewById(R.id.bt_1);
mBt2 = (Button) findViewById(R.id.bt2);
mBt3 = (Button) findViewById(R.id.bt3);
mFl = (FrameLayout) findViewById(R.id.fl);
mBt1.setOnClickListener(this);
mBt2.setOnClickListener(this);
mBt3.setOnClickListener(this);
}
@Override
public void onClick(View v) {
//隐藏全部fragment
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction
.hide(blankFragment)
.hide(blankFragment2)
.hide(blankFragment3)
;
switch (v.getId()) {
case R.id.bt_1:
fragmentTransaction.show(blankFragment);
setFragment(blankFragment);//如果有就设置到arrayList中
break;
case R.id.bt2:
fragmentTransaction.show(blankFragment2);
setFragment(blankFragment2);
break;
case R.id.bt3:
fragmentTransaction.show(blankFragment3);
setFragment(blankFragment3);
break;
}
//吧当前事务添加到回退栈中
// fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
}
private void setFragment(Fragment fragment) {
//判断是否有这个fragment
Log.d(TAG, "setFragment: list:"+list.size());
if (list.contains(fragment)) { //有
//移除，再添加
list.remove(fragment);
}
list.add(fragment);
}
@Override
public void onBackPressed() {
Log.d(TAG, "onDestroy: list.size"+list.size());
if (list.size()>1) {
//移除，最顶部那一个
list.remove(list.size()-1);
//显示最顶部那一个
showFragment(list.get(list.size()-1));
}else {
finish();
}
}
private void showFragment(Fragment fragment) {
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();//得到经理，并开始移动
fragmentTransaction
.hide(blankFragment)
.hide(blankFragment2)
.hide(blankFragment3)
;
fragmentTransaction.show(fragment);
fragmentTransaction.commit();
}
}
2.步骤
1.
//1.添加全部fragment，默认只显示1
blankFragment = new BlankFragment();
blankFragment2 = new BlankFragment2();
blankFragment3 = new BlankFragment3();
FragmentManager supportFragmentManager = getSupportFragmentManager();
mFragmentTransaction = supportFragmentManager.beginTransaction();
mFragmentTransaction
.add(R.id.fl, blankFragment, "blankFragment")//第三个参数表示标签
.add(R.id.fl, blankFragment2, "blankFragment2")
.add(R.id.fl, blankFragment3, "blankFragment3")
.hide(blankFragment2)
.hide(blankFragment3).commit();
2.显示那个fragment与添加到linkedList中
@Override
public void onClick(View v) {
//2.隐藏全部fragment
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction
.hide(blankFragment)
.hide(blankFragment2)
.hide(blankFragment3)
;
switch (v.getId()) {
case R.id.bt_1:
fragmentTransaction.show(blankFragment);
setFragment(blankFragment);//如果有就设置到LInkedList中
break;
case R.id.bt2:
fragmentTransaction.show(blankFragment2);
setFragment(blankFragment2);
break;
case R.id.bt3:
fragmentTransaction.show(blankFragment3);
setFragment(blankFragment3);
break;
}
fragmentTransaction.commit();
}
3.fragment添加到LinkedList方法
private void addFragment(Fragment fragment) {
//判断是否有这个fragment
Log.d(TAG, "setFragment: list:"+list.size());
if (list.contains(fragment)) { //有
//移除，再添加
list.remove(fragment);
}
list.add(fragment);
}
4.重写返回键，记得删掉super
@Override
public void onBackPressed() {
Log.d(TAG, "onDestroy: list.size"+list.size());
if (list.size()>1) {
//移除，最顶部那一个
list.remove(list.size()-1);//size已经减一了
//显示最顶部那一个
showFragment(list.get(list.size()-1));
}else {
finish();
}
}
5.回退后，实现上一个fragment的展示
private void showFragment(Fragment fragment) {
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();//得到经理，并开始移动
fragmentTransaction
.hide(blankFragment)
.hide(blankFragment2)
.hide(blankFragment3)
;
fragmentTransaction.show(fragment);
fragmentTransaction.commit();
}
3.问题：
- linkedList的增删有优势相对于arraylist
- list列表移除后，size会直接减一
