Android入门之Activity间互相传值详解
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介绍
今天的课程会比较好玩，我们在之前的Service篇章中看到了一种putExtras和getExtras来进行activity与service间的传值。而恰恰这种传值其实也是Android里的通用传值法。它同样可以适用在activity与activity间传值。
Android中的传值
传单个值
传多个值
具体我们来结合例子来看吧
课程目标
正向传值到下一个activity上
反向传值到调用activity上
- 正向传值用：Intent+Bundle传值；
- 反向传值我们使用：registerForActivityResult(new ActivityResultContracts.StartActivityForResult(), result -> {回调，并判断这个result.getResultCode()；
- 同时，我们制作了一个ActivityCollector extends Application来注册所有打开的activity，然后通过这个控制类来实现一键关闭所有打开的activity；
来看代码实现吧
全代码
前端
表格控制中用到的item_list.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="5dp">
<ImageView
android:id="@+id/iconImg"
android:layout_width="64dp"
android:layout_height="64dp"
android:layout_centerInParent="true"
android:class="lazy" data-src="@drawable/icon_1_128"
/>
<TextView
android:id="@+id/iconText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/iconImg"
android:layout_centerHorizontal="true"
android:layout_marginTop="30dp"
android:text="text"
android:textSize="18sp"
/>
</RelativeLayout>表格控制用到的GenericAdapter（这个在我们之前讲Adapter的篇章中已经写过）
package org.mk.android.demo;
import android.content.Context;
import android.util.Log;
import android.util.SparseArray;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
public abstract class
GenericAdapter <T> extends BaseAdapter {
private List<T> data;
private int layoutRes;
public GenericAdapter() {
}
public GenericAdapter(List<T> data, int layoutRes) {
this.data = data;
this.layoutRes = layoutRes;
}
@Override
public int getCount() {
Log.i("app",">>>>>>data.size: "+data.size());
if(data!=null) {
return data.size();
}
return 0;
}
@Override
public T getItem(int position) {
return data.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
Log.i("app",">>>>>>into getView");
ViewHolder holder = ViewHolder.bind(parent.getContext(), convertView, parent, layoutRes
, position);
bindView(holder, getItem(position));
return holder.getItemView();
}
//添加一个元素
public void add(T item) {
if (data == null) {
data = new ArrayList<>();
}
data.add(item);
notifyDataSetChanged();
}
//往特定位置，添加一个元素
public void add(int position,T item){
if (data == null) {
data = new ArrayList<>();
}
data.add(position, item);
notifyDataSetChanged();
}
public void remove(T item) {
if(data != null) {
data.remove(item);
}
notifyDataSetChanged();
}
public void remove(int position) {
if(data != null) {
data.remove(position);
}
notifyDataSetChanged();
}
public void clear() {
if(data != null) {
data.clear();
}
notifyDataSetChanged();
}
public abstract void bindView(ViewHolder holder, T obj);
public static class ViewHolder {
private SparseArray<View> mViews; //存储ListView 的 item中的View
private View item; //存放convertView
private int position; //游标
private Context context; //Context上下文
//构造方法，完成相关初始化
private ViewHolder(Context context, ViewGroup parent, int layoutRes) {
mViews = new SparseArray<>();
this.context = context;
View convertView = LayoutInflater.from(context).inflate(layoutRes, parent,false);
convertView.setTag(this);
item = convertView;
}
public static ViewHolder bind(Context context, View convertView, ViewGroup parent,
int layoutRes, int position) {
ViewHolder holder;
if(convertView == null) {
holder = new ViewHolder(context, parent, layoutRes);
} else {
holder = (ViewHolder) convertView.getTag();
holder.item = convertView;
}
holder.position = position;
return holder;
}
public <T extends View> T getView(int id) {
T t = (T) mViews.get(id);
if(t == null) {
t = (T) item.findViewById(id);
mViews.put(id, t);
}
return t;
}
public View getItemView() {
return item;
}
public int getItemPosition() {
return position;
}
public ViewHolder setText(int id, CharSequence text) {
View view = getView(id);
if(view instanceof TextView) {
((TextView) view).setText(text);
}
return this;
}
public ViewHolder setImageResource(int id, int drawableRes) {
View view = getView(id);
if(view instanceof ImageView) {
((ImageView) view).setImageResource(drawableRes);
} else {
view.setBackgroundResource(drawableRes);
}
return this;
}
public ViewHolder setTag(int id, Object obj) {
getView(id).setTag(obj);
return this;
}
public ImageView iconImg;
public TextView iconText;
}
}activity_home_page.xml文件
- activity_main.xml文件里点击【注册】按钮跳到activity_home_page.xml文件。
- 然后把activity_main.xml文件中的内容显示在activity_home_page.xml的toast中。
- 在activity_home_page.xml文件中选择一个图标后返回activity_main.xml，并显示用户选择的内容；
<?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"
android:padding="5dp"
tools:context=".HomePageActivity">
<!--numColumns设置每行显示多少个-->
<GridView
android:id="@+id/gridPhoto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:numColumns="3" />
</RelativeLayout>
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<TableRow>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="请输入注册信息："
android:textSize="18dp" />
</TableRow>
<TableRow>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="用户名："
android:textSize="18dp" />
<EditText
android:id="@+id/edTextLoginName"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:inputType="text"
android:text="" />
</TableRow>
<TableRow>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center_vertical"
android:text="性别："
android:textSize="18dp" />
<RadioGroup
android:id="@+id/rgGroup"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center_vertical"
android:orientation="horizontal">
<RadioButton
android:id="@+id/radioMan"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_marginRight="30dip"
android:text="男性" />
<RadioButton
android:id="@+id/radioWoman"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="女性" />
</RadioGroup>
</TableRow>
<TableRow>
<Button
android:id="@+id/buttonRegister"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_span="2"
android:text="注册"
android:textSize="18dp" />
</TableRow>
<TableRow>
<ImageView
android:id="@+id/selectedImg"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_span="2" />
</TableRow>
</TableLayout>后端代码
ActivityCollector
用于收集和一键关闭所有打开的Activity用
package org.mk.android.demo;
import android.app.Activity;
import android.app.Application;
import android.util.Log;
import java.util.LinkedList;
import java.util.List;
public class ActivityCollector extends Application {
//运用list来保存们每一个activity是关键
private List<Activity> mList = new LinkedList<Activity>();
//为了实现每次使用该类时不创建新的对象而创建的静态对象
private static ActivityCollector instance;
//构造方法
private ActivityCollector() {
}
//实例化一次
public synchronized static ActivityCollector getInstance() {
if (null == instance) {
instance = new ActivityCollector();
}
return instance;
}
//addActivity
public void addActivity(Activity activity) {
mList.add(activity);
}
//removeOneActivity
public void removeActivity(Activity activity) {
mList.remove(activity);
}
//关闭每一个list内的activity
public void exit() {
try {
if (mList != null && mList.size() > 0) {
Log.i("app", ">>>>>>activity size->" + mList.size());
for (Activity activity : mList) {
if (activity != null)
Log.i("app", ">>>>>>remove activity...");
activity.finish();
}
} else {
Log.i("app", ">>>>>>there is no activity need to be closed!");
}
} catch (Exception e) {
e.printStackTrace();
} finally {
System.exit(0);
}
}
//杀进程
public void onLowMemory() {
super.onLowMemory();
System.gc();
}
}IconBean.java
package org.mk.android.demo;
import java.io.Serializable;
public class IconBean implements Serializable {
public IconBean(int imgId, String iconText) {
this.imgId = imgId;
this.iconText = iconText;
}
private int imgId;
private String iconText = "";
public int getImgId() {
return imgId;
}
public void setImgId(int imgId) {
this.imgId = imgId;
}
public String getIconText() {
return iconText;
}
public void setIconText(String iconText) {
this.iconText = iconText;
}
}HomePageActivity.java
package org.mk.android.demo;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
public class HomePageActivity extends AppCompatActivity {
private String loginName;
private int gender;
private Context ctx;
private GridView gridPhoto;
private BaseAdapter adapter = null;
private List<IconBean> data = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home_page);
ActivityCollector.getInstance().addActivity(this);
Intent it = getIntent();
Bundle bd = it.getExtras();
loginName = bd.getString("loginName");
gender = bd.getInt("gender");
Toast.makeText(HomePageActivity.this, "当前输入内容，性别：" + gender + " 登录名:" + loginName, Toast.LENGTH_LONG).show();
gridPhoto = (GridView) findViewById(R.id.gridPhoto);
data = new ArrayList<IconBean>();
data.add(new IconBean(R.drawable.icon_1_128, "星爸爸"));
data.add(new IconBean(R.drawable.icon_2_128, "金拱门"));
data.add(new IconBean(R.drawable.icon_3_128, "机器人"));
data.add(new IconBean(R.drawable.icon_4_128, "小企鹅"));
data.add(new IconBean(R.drawable.icon_5_128, "凯瑞肯"));
data.add(new IconBean(R.drawable.icon_6_128, "小肥皂"));
data.add(new IconBean(R.drawable.icon_7_128, "流浪者"));
adapter = new GenericAdapter<IconBean>(data, R.layout.item_list) {
@Override
public void bindView(ViewHolder holder, IconBean obj) {
holder.setImageResource(R.id.iconImg, obj.getImgId());
holder.setText(R.id.iconText, obj.getIconText());
}
};
gridPhoto.setAdapter(adapter);
gridPhoto.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent it = getIntent();
Bundle bd = new Bundle();
bd.putInt("selectedId",data.get(position).getImgId());
bd.putString("selectedText",data.get(position).getIconText());
it.putExtras(bd);
setResult(101,it);
finish();
}
});
}
@Override
protected void onDestroy(){
super.onDestroy();
ActivityCollector.getInstance().removeActivity(this);
}
}MainActivity.java
package org.mk.android.demo;
import androidx.activity.result.ActivityResultLauncher;
import androidx.activity.result.contract.ActivityResultContracts;
import androidx.appcompat.app.AppCompatActivity;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.Toast;
import java.util.LinkedList;
public class MainActivity extends AppCompatActivity {
private Button buttonRegister;
private RadioGroup genderRG;
private EditText edTextLoginName;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ActivityCollector.getInstance().addActivity(this);
buttonRegister = (Button) findViewById(R.id.buttonRegister);
genderRG = (RadioGroup) findViewById(R.id.rgGroup);
edTextLoginName = (EditText) findViewById(R.id.edTextLoginName);
buttonRegister.setOnClickListener(new OnClickListener());
}
@Override
protected void onDestroy(){
super.onDestroy();
ActivityCollector.getInstance().exit();
}
//下面这段是配合着老式的startActivityForResult(homeIt,101);的写法，当我们用了registerForActivityResult
//下面这种onActivityResult就不需要写了。
//@Override
//protected void onActivityResult(int requestCode, int resultCode,
// Intent data) {
// super.onActivityResult(requestCode, resultCode, data);
// if (requestCode == 101 && resultCode == 101) {
// Bundle bd = data.getExtras();
// int imgid = bd.getInt("selectedId");
// String selectedContent = bd.getString("selectedText");
// ImageView img = (ImageView) findViewById(R.id.selectedImg);
// img.setImageResource(imgid);
// Toast.makeText(MainActivity.this, "你刚才选择的是：" + selectedContent,
// Toast.LENGTH_LONG).show();
// }
//}
private ActivityResultLauncher launcher = registerForActivityResult(new ActivityResultContracts.StartActivityForResult(), result -> {
if (result.getResultCode() == 101) {
Bundle bd = result.getData().getExtras();
int imgid = bd.getInt("selectedId");
String selectedContent = bd.getString("selectedText");
ImageView img = (ImageView) findViewById(R.id.selectedImg);
img.setImageResource(imgid);
Toast.makeText(MainActivity.this, "你刚才选择的是：" + selectedContent, Toast.LENGTH_LONG).show();
}
});
private class OnClickListener implements View.OnClickListener {
private int gender = -1;
private String loginName = "";
@Override
public void onClick(View v) {
for (int i = 0; i < genderRG.getChildCount(); i++) {
RadioButton rb = (RadioButton) genderRG.getChildAt(i);
if (rb.isChecked()) {
switch (i) {
case 0:
gender = 0;
break;
case 1:
gender = 1;
break;
}
break;
}
}
loginName = edTextLoginName.getText().toString();
//Toast.makeText(MainActivity.this, "当前输入内容，性别：" + gender + "
// 登录名: " + loginName, Toast.LENGTH_SHORT).show();
Log.i("app", "当前输入内容，性别：" + gender + " 登录名:" + loginName);
transferToHomePage(loginName, gender);
}
private void transferToHomePage(String loginName, int gender) {
Intent homeIt = new Intent(MainActivity.this, HomePageActivity.class);
Bundle bd = new Bundle();
bd.putString("loginName", loginName);
bd.putInt("gender", gender);
homeIt.putExtras(bd);
//startActivity(homeIt);
//startActivityForResult(homeIt,101);
// 这种写法已经废弃用新的registerForActivityResult会非常优雅且不用去覆盖onActivityResult
launcher.launch(homeIt);
}
}
}
传递值到子activity-HomePageActivity里使用putExtras自然没得话说。关键在于我们运行sub activity的launcher.launch(homeIt);方法。这个方法通过一个registerForActivityResult(new ActivityResultContracts.StartActivityForResult(), result ->来判断当子activity返回即调用了finish()生命周期后，可以得到子activity在finish()语句前setResult(101,it);中的内容即实现了子activity中的值回传上一层activity了。
自己请动一下手试试看吧。
附、工程结构
到此这篇关于Android入门之Activity间互相传值详解的文章就介绍到这了,更多相关Android Activity互相传值内容请搜索编程网以前的文章或继续浏览下面的相关文章希望大家以后多多支持编程网！
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