Question

如果我有3个片段，如frag-1，frag-2，frag-3，我确实在每个片段中都有3个片段的链接。每当我再次访问先前打开的片段时，我只需要重用或不重新创建新实例。就像我从frag-1开始然后我打开frag-2然后我打开frag-3再次打开frag-2然后我应该得到之前的实例而不是获得新的实例。就像在活动中一样，我们可以使用启动模式，例如，单个任务不允许创建新对象，它将重用来自后栈的现有对象。

编辑：添加了代码

package com.example.fragmentexample1;

import java.util.List;

import android.annotation.TargetApi;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.Context;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

import com.example.fragments.Fragment1;
import com.example.fragments.Fragment2;
import com.example.fragments.Fragment3;

public class MainActivity extends ActionBarActivity implements OnClickListener {

    private Button btn1, btn2, btn3;
    private Fragment1 frag1;
    private Fragment2 frag2;
    private Fragment3 frag3;

    @TargetApi(Build.VERSION_CODES.KITKAT)
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        btn1 = (Button) findViewById(R.id.btn1);
        btn2 = (Button) findViewById(R.id.btn2);
        btn3 = (Button) findViewById(R.id.btn3);
        btn1.setOnClickListener(this);
        btn2.setOnClickListener(this);
        btn3.setOnClickListener(this);

        frag1 = new Fragment1();
        frag2 = new Fragment2();
        frag3 = new Fragment3();

    }

    @Override
    public void onClick(View v) {
        if (v.getId() == btn1.getId()) {
            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            transaction.replace(R.id.lin2, frag1);
            transaction.addToBackStack(null);
            transaction.commit();

        } else if (v.getId() == btn2.getId()) {
            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            transaction.replace(R.id.lin2, frag2);
            transaction.addToBackStack(null);
            transaction.commit();
        } else if (v.getId() == btn3.getId()) {
            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            transaction.replace(R.id.lin2, frag3);
            transaction.addToBackStack(null);
            transaction.commit();
        }
    }

}

布局XML：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <ListView
        android:id="@+id/tempList"
        android:layout_width="match_parent"
        android:layout_height="100dp" />

    <Button
        android:id="@+id/btn1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add" />

    <Button
        android:id="@+id/btn2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="OpenFragment2" />

    <Button
        android:id="@+id/btn3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="OpenFragment3" />

    <LinearLayout
        android:id="@+id/lin2"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical" >


    </LinearLayout>

</LinearLayout>

片段1的布局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:orientation="vertical" >


    <TextView 
        android:id="@+id/txt1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Fragment ONE!!!"
        />

    <EditText 
        android:id="@+id/ed1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp"
        />

</LinearLayout>

从backstack重用片段

0 个答案: