深海游弋的鱼 – 默默的点滴

最近在使用官方的 Android Jetpack 库的时候，发现 Activity/Fragment 都有对应的 lifecycle（生命周期） 组件，比如ViewModel。唯独 Dialog 没有对应的组件，感觉非常奇怪。

搜索了一通，发现官方推荐 DialogFragment 替代直接使用 Dialog 。 DialogFragment 在 Android 3.0 时被引入，是一种特殊的 Fragment ，用于在 Activity 的内容之上展示一个模态的对话框。典型的用于：展示警告框，输入框，确认框等等。

在 DialogFragment 产生之前，我们创建对话框：一般采用 AlertDialog 和 Dialog 。注意：官方不推荐直接使用Dialog创建对话框。

另外，更常见的在 logcat 中经常看到输出由于 Dialog 引起的 WindowLeaked 日志，这个日志产生的原因就是 Dialog 显示所依赖的 Activity 被销毁/重建的时候没有关闭显示在上层的 Dialog 。但是很多时候我们不方便在 Activity 的 onDestroy() 中查找全部的 Dialog 来逐个关闭，尤其是依赖的 Activity 是第三方的 SDK 创建的情况下。这种情况下，DialogFragment 不失为一个好的替代选项。

好处与用法

使用DialogFragment来管理对话框，当旋转屏幕和按下后退键时可以更好的管理其声明周期，它和Fragment有着基本一致的生命周期。且DialogFragment也允许开发者把Dialog作为内嵌的组件进行重用，类似Fragment（可以在大屏幕和小屏幕显示出不同的效果）。下面会通过例子展示这些好处~

使用DialogFragment至少需要实现onCreateView或者onCreateDIalog方法。onCreateView即使用定义的xml布局文件展示Dialog。onCreateDialog即利用AlertDialog或者Dialog创建出Dialog。

重写onCreateView创建Dialog

a)布局文件，我们创建一个设置名称的布局文件：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" >
 
    <TextView
        android:id="@+id/id_label_your_name"
        android:layout_width="wrap_content"
        android:layout_height="32dp"
        android:gravity="center_vertical"
        android:text="Your name:" />
 
    <EditText
        android:id="@+id/id_txt_your_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/id_label_your_name"
        android:imeOptions="actionDone"
        android:inputType="text" />
 
    <Button
        android:id="@+id/id_sure_edit_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_below="@id/id_txt_your_name"
        android:text="ok" />
 
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="wrap_content"

android:layout_height="wrap_content" >

<TextView

android:id="@+id/id_label_your_name"

android:layout_width="wrap_content"

android:layout_height="32dp"

android:gravity="center_vertical"

android:text="Your name:" />

<EditText

android:id="@+id/id_txt_your_name"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_toRightOf="@id/id_label_your_name"

android:imeOptions="actionDone"

android:inputType="text" />

<Button

android:id="@+id/id_sure_edit_name"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentRight="true"

android:layout_below="@id/id_txt_your_name"

android:text="ok" />

</RelativeLayout>

b)继承DialogFragment，重写onCreateView方法

package com.example.zhy_dialogfragment;
 
import android.app.DialogFragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
 
public class EditNameDialogFragment extends DialogFragment {
 
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
        final View view = inflater.inflate(R.layout.fragment_edit_name, container);
        return view;
    }
}

package com.example.zhy_dialogfragment;

import android.app.DialogFragment;

import android.os.Bundle;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

public class EditNameDialogFragment extends DialogFragment {

@Override

public View onCreateView(LayoutInflater inflater, ViewGroup container,

Bundle savedInstanceState) {

final View view = inflater.inflate(R.layout.fragment_edit_name, container);

return view;

}

c)测试运行：
Main方法中调用：

public void showEditDialog(View view) {
    final EditNameDialogFragment editNameDialog = new EditNameDialogFragment();
    editNameDialog.show(getFragmentManager(), "EditNameDialog");
}

public void showEditDialog(View view) {

final EditNameDialogFragment editNameDialog = new EditNameDialogFragment();

editNameDialog.show(getFragmentManager(), "EditNameDialog");

}

效果图：

可以看到，对话框成功创建并显示出来，不过默认对话框有个讨厌的标题，我们怎么去掉呢：可以在onCreateView中调用getDialog().requestWindowFeature(Window.FEATURE_NO_TITLE);即可去掉。即：

public class EditNameDialogFragment extends DialogFragment {
 
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
        getDialog().requestWindowFeature(Window.FEATURE_NO_TITLE);
        final View view = inflater.inflate(R.layout.fragment_edit_name, container);
        return view;
    }
}

public class EditNameDialogFragment extends DialogFragment {

@Override

public View onCreateView(LayoutInflater inflater, ViewGroup container,

Bundle savedInstanceState) {

getDialog().requestWindowFeature(Window.FEATURE_NO_TITLE);

final View view = inflater.inflate(R.layout.fragment_edit_name, container);

return view;

}

效果图：

很完美的去掉了讨厌的标题。

重写onCreateDialog创建Dialog

在 onCreateDialog 中一般可以使用 AlertDialog 或者 Dialog 创建对话框，不过既然 Google 不推荐直接使用 Dialog，我们就使用 AlertDialog 来创建一个登录的对话框。
a)布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical" >
 
    <ImageView
        android:layout_width="match_parent"
        android:layout_height="64dp"
        android:background="#FFFFBB33"
        android:contentDescription="@string/app_name"
        android:scaleType="center"
        android:src="@drawable/title" />
 
    <EditText
        android:id="@+id/id_txt_username"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="4dp"
        android:layout_marginLeft="4dp"
        android:layout_marginRight="4dp"
        android:layout_marginTop="16dp"
        android:hint="input username"
        android:inputType="textEmailAddress" />
 
    <EditText
        android:id="@+id/id_txt_password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="16dp"
        android:layout_marginLeft="4dp"
        android:layout_marginRight="4dp"
        android:layout_marginTop="4dp"
        android:fontFamily="sans-serif"
        android:hint="input password"
        android:inputType="textPassword" />
 
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:orientation="vertical" >

<ImageView

android:layout_width="match_parent"

android:layout_height="64dp"

android:background="#FFFFBB33"

android:contentDescription="@string/app_name"

android:scaleType="center"

android:src="@drawable/title" />

<EditText

android:id="@+id/id_txt_username"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_marginBottom="4dp"

android:layout_marginLeft="4dp"

android:layout_marginRight="4dp"

android:layout_marginTop="16dp"

android:hint="input username"

android:inputType="textEmailAddress" />

<EditText

android:id="@+id/id_txt_password"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_marginBottom="16dp"

android:layout_marginLeft="4dp"

android:layout_marginRight="4dp"

android:layout_marginTop="4dp"

android:fontFamily="sans-serif"

android:hint="input password"

android:inputType="textPassword" />

</LinearLayout>

b)继承 DialogFragment 重写 onCreateDialog 方法

package com.example.zhy_dialogfragment;
 
import android.app.AlertDialog;
import android.app.Dialog;
import android.app.DialogFragment;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
 
public class LoginDialogFragment extends DialogFragment {
 
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        final AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        // Get the layout inflater
        final LayoutInflater inflater = getActivity().getLayoutInflater();
        final View view = inflater.inflate(R.layout.fragment_login_dialog, null);
        // Inflate and set the layout for the dialog
        // Pass null as the parent view because its going in the dialog layout
        builder.setView(view)
            // Add action buttons
            .setPositiveButton("Sign in",
                new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int id) {
                    }
                }).setNegativeButton("Cancel", null);
        return builder.create();
    }
}

package com.example.zhy_dialogfragment;

import android.app.AlertDialog;

import android.app.Dialog;

import android.app.DialogFragment;

import android.content.DialogInterface;

import android.os.Bundle;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.EditText;

public class LoginDialogFragment extends DialogFragment {

@Override

public Dialog onCreateDialog(Bundle savedInstanceState) {

final AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());

// Get the layout inflater

final LayoutInflater inflater = getActivity().getLayoutInflater();

final View view = inflater.inflate(R.layout.fragment_login_dialog, null);

// Inflate and set the layout for the dialog

// Pass null as the parent view because its going in the dialog layout

builder.setView(view)

// Add action buttons

.setPositiveButton("Sign in",

new DialogInterface.OnClickListener() {

@Override

public void onClick(DialogInterface dialog, int id) {

}

}).setNegativeButton("Cancel", null);

return builder.create();

}

c)调用

public void showLoginDialog(View view) {
    final LoginDialogFragment dialog = new LoginDialogFragment();
    dialog.show(getFragmentManager(), "loginDialog");
}

public void showLoginDialog(View view) {

final LoginDialogFragment dialog = new LoginDialogFragment();

dialog.show(getFragmentManager(), "loginDialog");

}

效果图：

可以看到通过重写 onCreateDialog 同样可以实现创建对话框，效果还是很nice的。

传递数据给Activity

从dialog传递数据给Activity，可以使用“fragment interface pattern”的方式，下面通过一个改造上面的登录框来展示这种模式。

改动比较小，直接贴代码了：

package com.example.zhy_dialogfragment;
 
import android.app.AlertDialog;
import android.app.Dialog;
import android.app.DialogFragment;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
 
public class LoginDialogFragment extends DialogFragment {
    private EditText mUsername;
    private EditText mPassword;
 
    public interface LoginInputListener {
        void onLoginInputComplete(String username, String password);
    }
	
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        final AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        // Get the layout inflater
        final LayoutInflater inflater = getActivity().getLayoutInflater();
        final View view = inflater.inflate(R.layout.fragment_login_dialog, null);
        mUsername = (EditText) view.findViewById(R.id.id_txt_username);
        mPassword = (EditText) view.findViewById(R.id.id_txt_password);
        // Inflate and set the layout for the dialog
        // Pass null as the parent view because its going in the dialog layout
        builder.setView(view)
            // Add action buttons
            .setPositiveButton("Sign in",
                new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int id) {
                        final LoginInputListener listener = (LoginInputListener) getActivity();
                        listener.onLoginInputComplete(mUsername.getText().toString(), mPassword.getText().toString());
                    }
                }).setNegativeButton("Cancel", null);
        return builder.create();
    }
}

package com.example.zhy_dialogfragment;

import android.app.AlertDialog;

import android.app.Dialog;

import android.app.DialogFragment;

import android.content.DialogInterface;

import android.os.Bundle;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.EditText;

public class LoginDialogFragment extends DialogFragment {

private EditText mUsername;

private EditText mPassword;

public interface LoginInputListener {

void onLoginInputComplete(String username, String password);

}

@Override

public Dialog onCreateDialog(Bundle savedInstanceState) {

final AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());

// Get the layout inflater

final LayoutInflater inflater = getActivity().getLayoutInflater();

final View view = inflater.inflate(R.layout.fragment_login_dialog, null);

mUsername = (EditText) view.findViewById(R.id.id_txt_username);

mPassword = (EditText) view.findViewById(R.id.id_txt_password);

// Inflate and set the layout for the dialog

// Pass null as the parent view because its going in the dialog layout

builder.setView(view)

// Add action buttons

.setPositiveButton("Sign in",

new DialogInterface.OnClickListener() {

@Override

public void onClick(DialogInterface dialog, int id) {

final LoginInputListener listener = (LoginInputListener) getActivity();

listener.onLoginInputComplete(mUsername.getText().toString(), mPassword.getText().toString());

}

}).setNegativeButton("Cancel", null);

return builder.create();

}

拿到username和password的引用，在点击登录的时候，把activity强转为我们自定义的接口：LoginInputListener，然后将用户输入的数据返回。
MainActivity中需要实现我们的接口LoginInputListener，实现我们的方法，就可以实现当用户点击登陆时，获得我们的帐号密码了：

package com.example.zhy_dialogfragment;
 
import com.example.zhy_dialogfragment.LoginDialogFragment.LoginInputListener;
 
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Toast;
 
public class MainActivity extends Activity implements LoginInputListener {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
 
    public void showLoginDialog(View view) {
        final LoginDialogFragment dialog = new LoginDialogFragment();
        dialog.show(getFragmentManager(), "loginDialog");
    }
 
    @Override
    public void onLoginInputComplete(String username, String password) {
        Toast.makeText(this, "帐号：" + username + ",  密码 :" + password,
				Toast.LENGTH_SHORT).show();
    }
}

package com.example.zhy_dialogfragment;

import com.example.zhy_dialogfragment.LoginDialogFragment.LoginInputListener;

import android.app.Activity;

import android.app.AlertDialog;

import android.content.DialogInterface;

import android.os.Bundle;

import android.view.LayoutInflater;

import android.view.View;

import android.widget.Toast;

public class MainActivity extends Activity implements LoginInputListener {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

}

public void showLoginDialog(View view) {

final LoginDialogFragment dialog = new LoginDialogFragment();

dialog.show(getFragmentManager(), "loginDialog");

}

@Override

public void onLoginInputComplete(String username, String password) {

Toast.makeText(this, "帐号：" + username + ", 密码 :" + password,

Toast.LENGTH_SHORT).show();

}

效果：

DialogFragment做屏幕适配

我们希望，一个对话框在大屏幕上以对话框的形式展示，而小屏幕上则直接嵌入当前的Actvity中。这种效果的对话框，只能通过重写onCreateView实现。下面我们利用上面的EditNameDialogFragment来显示。

EditNameDialogFragment我们已经编写好了，直接在MainActivity中写调用

public void showDialogInDifferentScreen(View view) {
    final FragmentManager fragmentManager = getFragmentManager();
    final EditNameDialogFragment newFragment = new EditNameDialogFragment();
 
    final boolean mIsLargeLayout = getResources().getBoolean(R.bool.large_layout) ;
    Log.e("TAG", mIsLargeLayout+"");
    if (mIsLargeLayout ) {
        // The device is using a large layout, so show the fragment as a
        // dialog
        newFragment.show(fragmentManager, "dialog");
    } else {
        // The device is smaller, so show the fragment fullscreen
        final FragmentTransaction transaction = fragmentManager.beginTransaction();
        // For a little polish, specify a transition animation
        transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
        // To make it fullscreen, use the 'content' root view as the
        // container
        // for the fragment, which is always the root view for the activity
        transaction.replace(R.id.id_ly, newFragment).commit();
    }
}

public void showDialogInDifferentScreen(View view) {

final FragmentManager fragmentManager = getFragmentManager();

final EditNameDialogFragment newFragment = new EditNameDialogFragment();

final boolean mIsLargeLayout = getResources().getBoolean(R.bool.large_layout) ;

Log.e("TAG", mIsLargeLayout+"");

if (mIsLargeLayout ) {

// The device is using a large layout, so show the fragment as a

// dialog

newFragment.show(fragmentManager, "dialog");

} else {

// The device is smaller, so show the fragment fullscreen

final FragmentTransaction transaction = fragmentManager.beginTransaction();

// For a little polish, specify a transition animation

transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);

// To make it fullscreen, use the 'content' root view as the

// container

// for the fragment, which is always the root view for the activity

transaction.replace(R.id.id_ly, newFragment).commit();

}

可以看到，我们通过读取R.bool.large_layout，然后根据得到的布尔值，如果是大屏幕则直接以对话框显示，如果是小屏幕则嵌入我们的Activity布局中
这个R.bool.large_layout是我们定义的资源文件：

在默认的values下新建一个bools.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
 
    <bool name="large_layout">false</bool>
 
</resources>

<?xml version="1.0" encoding="utf-8"?>

<bool name="large_layout">false</bool>

</resources>

然后在res下新建一个values-large，在values-large下再新建一个bools.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
 
    <bool name="large_layout">true</bool>
 
</resources>

<?xml version="1.0" encoding="utf-8"?>

</resources>

最后测试：

左边为模拟器，右边为我的手机~~~~~

屏幕旋转

当用户输入帐号密码时，忽然旋转了一下屏幕，帐号密码不见了~~~是不是会抓狂

传统的 new AlertDialog 在屏幕旋转时，第一不会保存用户输入的值，第二还会报异常，因为 Activity 销毁前不允许对话框未关闭。而通过 DialogFragment 实现的对话框则可以完全不必考虑旋转的问题。

我们直接把上面登录使用 AlertDialog 创建的登录框，拷贝到 MainActivity 中直接调用：

public void showLoginDialogWithoutFragment(View view) {
    final AlertDialog.Builder builder = new AlertDialog.Builder(this);
    // Get the layout inflater
    final LayoutInflater inflater = this.getLayoutInflater();
 
    // Inflate and set the layout for the dialog
    // Pass null as the parent view because its going in the dialog layout
    builder.setView(inflater.inflate(R.layout.fragment_login_dialog, null))
        // Add action buttons
        .setPositiveButton("Sign in",
            new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int id) {
                    // sign in the user ...
                }
            }).setNegativeButton("Cancel", null).show();
    }

public void showLoginDialogWithoutFragment(View view) {

final AlertDialog.Builder builder = new AlertDialog.Builder(this);

// Get the layout inflater

final LayoutInflater inflater = this.getLayoutInflater();

// Inflate and set the layout for the dialog

// Pass null as the parent view because its going in the dialog layout

builder.setView(inflater.inflate(R.layout.fragment_login_dialog, null))

// Add action buttons

.setPositiveButton("Sign in",

new DialogInterface.OnClickListener() {

@Override

public void onClick(DialogInterface dialog, int id) {

// sign in the user ...

}

}).setNegativeButton("Cancel", null).show();

}

下面我分别点击两种方式创建的登录框，看效果图：

可以看到，传统的Dialog旋转屏幕时就消失了，且后台log会报异常~~~使用DialogFragment则不受影响。

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日期: 2022 年 6 月 27 日

macOS Big Sur(11.6.7/Intel CPU)编译Android/iOS/macOS版本的RocksDB 6.29.5

参考链接

Android官方推荐: DialogFragment创建对话框

好处与用法

重写onCreateView创建Dialog

重写onCreateDialog创建Dialog

传递数据给Activity

DialogFragment做屏幕适配

屏幕旋转

参考链接