Android入門之Activity間互相傳值詳解
介紹
今天的課程會比較好玩,我們在之前的Service篇章中看到了一種putExtras和getExtras來進(jìn)行activity與service間的傳值。而恰恰這種傳值其實(shí)也是Android里的通用傳值法。它同樣可以適用在activity與activity間傳值。
Android中的傳值
傳單個(gè)值
傳多個(gè)值
具體我們來結(jié)合例子來看吧
課程目標(biāo)
正向傳值到下一個(gè)activity上
反向傳值到調(diào)用activity上
- 正向傳值用:Intent+Bundle傳值;
- 反向傳值我們使用:registerForActivityResult(new ActivityResultContracts.StartActivityForResult(), result -> {回調(diào),并判斷這個(gè)result.getResultCode();
- 同時(shí),我們制作了一個(gè)ActivityCollector extends Application來注冊所有打開的activity,然后通過這個(gè)控制類來實(shí)現(xiàn)一鍵關(guān)閉所有打開的activity;
來看代碼實(shí)現(xiàn)吧
全代碼
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: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(這個(gè)在我們之前講Adapter的篇章中已經(jīng)寫過)
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(); } //添加一個(gè)元素 public void add(T item) { if (data == null) { data = new ArrayList<>(); } data.add(item); notifyDataSetChanged(); } //往特定位置,添加一個(gè)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; //存儲ListView 的 item中的View private View item; //存放convertView private int position; //游標(biāo) private Context context; //Context上下文 //構(gòu)造方法,完成相關(guān)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; } /** * 獲取當(dāng)前條目 */ public View getItemView() { return item; } /** * 獲取條目位置 */ public int getItemPosition() { return position; } /** * 設(shè)置文字 */ public ViewHolder setText(int id, CharSequence text) { View view = getView(id); if(view instanceof TextView) { ((TextView) view).setText(text); } return this; } /** * 設(shè)置圖片 */ 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; } /** * 設(shè)置標(biāo)簽 */ 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文件里點(diǎn)擊【注冊】按鈕跳到activity_home_page.xml文件。
- 然后把a(bǔ)ctivity_main.xml文件中的內(nèi)容顯示在activity_home_page.xml的toast中。
- 在activity_home_page.xml文件中選擇一個(gè)圖標(biāo)后返回activity_main.xml,并顯示用戶選擇的內(nèi)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設(shè)置每行顯示多少個(gè)--> <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="請輸入注冊信息:" android:textSize="18dp" /> </TableRow> <TableRow> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="用戶名:" 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="性別:" 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="注冊" 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>
后端代碼
ActivityCollector
用于收集和一鍵關(guān)閉所有打開的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 { //運(yùn)用list來保存?zhèn)兠恳粋€(gè)activity是關(guān)鍵 private List<Activity> mList = new LinkedList<Activity>(); //為了實(shí)現(xiàn)每次使用該類時(shí)不創(chuàng)建新的對象而創(chuàng)建的靜態(tài)對象 private static ActivityCollector instance; //構(gòu)造方法 private ActivityCollector() { } //實(shí)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); } //關(guān)閉每一個(gè)list內(nèi)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); } } //殺進(jìn)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, "當(dāng)前輸入內(nèi)容,性別:" + gender + " 登錄名:" + 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, "金拱門")); data.add(new IconBean(R.drawable.icon_3_128, "機(jī)器人")); data.add(new IconBean(R.drawable.icon_4_128, "小企鵝")); data.add(new IconBean(R.drawable.icon_5_128, "凱瑞肯")); 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(); } //下面這段是配合著老式的startActivityForResult(homeIt,101);的寫法,當(dāng)我們用了registerForActivityResult //下面這種onActivityResult就不需要寫了。 //@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, "你剛才選擇的是:" + 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, "你剛才選擇的是:" + 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, "當(dāng)前輸入內(nèi)容,性別:" + gender + " // 登錄名: " + loginName, Toast.LENGTH_SHORT).show(); Log.i("app", "當(dāng)前輸入內(nèi)容,性別:" + gender + " 登錄名:" + 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); // 這種寫法已經(jīng)廢棄用新的registerForActivityResult會非常優(yōu)雅且不用去覆蓋onActivityResult launcher.launch(homeIt); } } }
傳遞值到子activity-HomePageActivity里使用putExtras自然沒得話說。關(guān)鍵在于我們運(yùn)行sub activity的launcher.launch(homeIt);方法。這個(gè)方法通過一個(gè)registerForActivityResult(new ActivityResultContracts.StartActivityForResult(), result ->來判斷當(dāng)子activity返回即調(diào)用了finish()生命周期后,可以得到子activity在finish()語句前setResult(101,it);中的內(nèi)容即實(shí)現(xiàn)了子activity中的值回傳上一層activity了。
自己請動(dòng)一下手試試看吧。
附、工程結(jié)構(gòu)
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