Fragment 返回键处理

本文最后更新于:4 年前

逻辑

启动后进入 FirstFragment,在 FirstFragment 按返回键退出,可以通过点击按钮显示 SecondFragment、ThirdFragment、FourthFragment:

  • 进入 SecondFragment 后,按返回键返回 FirstFragment,但是不更新 FirstFragment。
  • 进入 ThirdFragment 后,按返回键退出,可以通过点击按钮显示 FourthFragment。
  • 进入 FourthFragment 后,按返回键返回 FirstFragment 或 ThirdFragment(取决于从 FirstFragment 或 ThirdFragment 进入),同时更新 FirstFragment 或 ThirdFragment。

点击按钮显示不同 Fragment

布局文件

  • fragment_first.xml
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<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="io.weichao.fragment_demo.activity.MainActivity">

<TextView
android:id="@+id/tv_time"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />

<Button
android:id="@+id/btn_change2SecondFragment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/tv_time"
android:text="@string/change2SecondFragment" />

<Button
android:id="@+id/btn_change2ThirdFragment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/btn_change2SecondFragment"
android:text="@string/change2ThirdFragment" />

<Button
android:id="@+id/btn_change2FourthFragment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/btn_change2ThirdFragment"
android:text="@string/change2FourthFragment" />
</RelativeLayout>

添加点击监听

  • FirstFragment.java
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public class FirstFragment extends Fragment {
private Button mChange2SecondFragmentBtn;
private Button mChange2ThirdFragmentBtn;
private Button mChange2FourthFragmentBtn;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
RelativeLayout rootView = (RelativeLayout) inflater.inflate(R.layout.fragment_first, null);
mChange2SecondFragmentBtn = rootView.findViewById(R.id.btn_change2SecondFragment);
mChange2ThirdFragmentBtn = rootView.findViewById(R.id.btn_change2ThirdFragment);
mChange2FourthFragmentBtn = rootView.findViewById(R.id.btn_change2FourthFragment);
return rootView;
}

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mChange2SecondFragmentBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (mMainActivity != null) {
mMainActivity.change2SecondFragment();
} else {
Log.e(TAG, "mMainActivity == null");
}
}
});
mChange2ThirdFragmentBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (mMainActivity != null) {
mMainActivity.change2ThirdFragment();
} else {
Log.e(TAG, "mMainActivity == null");
}
}
});
mChange2FourthFragmentBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (mMainActivity != null) {
mMainActivity.change2FourthFragment();
} else {
Log.e(TAG, "mMainActivity == null");
}
}
});
}
}

添加点击响应

  • MainActivity.java
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public class MainActivity extends AppCompatActivity {
private Fragment mBeforeFragment;
private Fragment mFragment;

public void change2FirstFragment() {
FirstFragment fragment = (FirstFragment) getSupportFragmentManager().findFragmentByTag("FirstFragment");
if (fragment == null) {
fragment = FirstFragment.newInstance(this);
Bundle bundle = new Bundle();
bundle.putString("time", DateUtil.getCurrentTime());
fragment.setArguments(bundle);
FragmentUtil.addFragment(getSupportFragmentManager(), R.id.fragment, mFragment, fragment, "FirstFragment");
} else {
if (mFragment != fragment) {
FragmentUtil.showFragment(getSupportFragmentManager(), mFragment, fragment);
}
fragment.update(DateUtil.getCurrentTime());
}
mBeforeFragment = null;
mFragment = fragment;
}

public void change2SecondFragment() {
SecondFragment fragment = (SecondFragment) getSupportFragmentManager().findFragmentByTag("SecondFragment");
if (fragment == null) {
fragment = SecondFragment.newInstance(this);
Bundle bundle = new Bundle();
bundle.putString("time", DateUtil.getCurrentTime());
fragment.setArguments(bundle);
FragmentUtil.addFragment(getSupportFragmentManager(), R.id.fragment, mFragment, fragment, "SecondFragment");
} else {
if (mFragment != fragment) {
FragmentUtil.showFragment(getSupportFragmentManager(), mFragment, fragment);
}
fragment.update(DateUtil.getCurrentTime());
}
mBeforeFragment = mFragment;
mFragment = fragment;
}

public void change2ThirdFragment() {
ThirdFragment fragment = (ThirdFragment) getSupportFragmentManager().findFragmentByTag("ThirdFragment");
if (fragment == null) {
fragment = ThirdFragment.newInstance(this);
Bundle bundle = new Bundle();
bundle.putString("time", DateUtil.getCurrentTime());
fragment.setArguments(bundle);
FragmentUtil.addFragment(getSupportFragmentManager(), R.id.fragment, mFragment, fragment, "ThirdFragment");
} else {
if (mFragment != fragment) {
FragmentUtil.showFragment(getSupportFragmentManager(), mFragment, fragment);
}
fragment.update(DateUtil.getCurrentTime());
}
mBeforeFragment = null;
mFragment = fragment;
}

public void change2FourthFragment() {
FourthFragment fragment = (FourthFragment) getSupportFragmentManager().findFragmentByTag("FourthFragment");
if (fragment == null) {
fragment = FourthFragment.newInstance(this);
Bundle bundle = new Bundle();
bundle.putString("time", DateUtil.getCurrentTime());
fragment.setArguments(bundle);
FragmentUtil.addFragment(getSupportFragmentManager(), R.id.fragment, mFragment, fragment, "FourthFragment");
} else {
if (mFragment != fragment) {
FragmentUtil.showFragment(getSupportFragmentManager(), mFragment, fragment);
}
fragment.update(DateUtil.getCurrentTime());
}
mBeforeFragment = mFragment;
mFragment = fragment;
}
}

返回键逻辑实现

  • MainActivity.java
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@Override
public void onBackPressed() {
if (mBeforeFragment == null) {
finish();
} else if (mFragment instanceof SecondFragment) {
FragmentUtil.showFragment(getSupportFragmentManager(), mFragment, mBeforeFragment);
mFragment = mBeforeFragment;
mBeforeFragment = null;
} else if (mFragment instanceof FourthFragment) {
if (mBeforeFragment instanceof FirstFragment) {
change2FirstFragment();
} else if (mBeforeFragment instanceof ThirdFragment) {
change2ThirdFragment();
}
}
}

源码地址



Fragment 返回键处理
https://weichao.io/f13422ee9694/
作者
魏超
发布于
2017年12月31日
更新于
2018年12月7日
许可协议