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2015-10-09

Android - Activity 傳遞自訂物件參數

2015-10-09 8:14 PM

傳遞字串, 數字等參數的方法我想大家應該都沒問題

但 Intent 就是沒有 putExtra( Object ); 的方法

用 Serializable 又會出現錯誤訊息 而且其實有點偷吃步

正確的方法是應該使用 Parcelable 這個介面來完成

首先須實作 Parcelable 介面

  1. public class ArticleBean implements Parcelable

並在 writeToParcel 將欄位值寫入 Parcel 內

  1. @Override
  2. public void writeToParcel(Parcel dest, int flags) {
  3.  dest.writeInt(serialNumber);
  4.  dest.writeString(boardTitle);
  5.  dest.writeString(aid);
  6.  dest.writeString(title);
  7.  dest.writeString(status);
  8.  dest.writeString(pushes);
  9.  dest.writeString(category);
  10.  dest.writeString(author);
  11.  dest.writeString(date);
  12.  dest.writeBooleanArray( new boolean[]{online, read, changed, locked, connected, mail} );
  13.  dest.writeString( articleType.getValue() );
  14.  dest.writeString(articleHeader.getValue());
  15. }

然後再新增一個 static 的 CREATOR 讓參數可以被重新產生

是的 傳遞到另一個 Activity 的參數是重新產生過的新物件

  1. public static final Parcelable.Creator<ArticleBean> CREATOR = new Parcelable.Creator<ArticleBean>() {
  2.  public ArticleBean createFromParcel(Parcel parcel) {
  3.      return new ArticleBean(parcel);
  4.  }
  5.  
  6.  public ArticleBean[] newArray(int size) {
  7.      return new ArticleBean[size];
  8.  }
  9. };

最後再新增一個使用 Parcel 創建的建構子

重點是所有參數不論型態皆須依照你放入的順序依次取出

例如你第一個放的是字串 第一個取出來的就必須是字串

如果你取得 boolean 他就會報錯

  1. private ArticleBean(Parcel parcel) {
  2.  boolean[] booleans = new boolean[6];
  3.  
  4.  serialNumber = parcel.readInt();
  5.  boardTitle = parcel.readString();
  6.  aid = parcel.readString();
  7.  title = parcel.readString();
  8.  status = parcel.readString();
  9.  pushes = parcel.readString();
  10.  category = parcel.readString();
  11.  author = parcel.readString();
  12.  date = parcel.readString();
  13.  
  14.  parcel.readBooleanArray(booleans);
  15.  
  16.  online = booleans[0];
  17.  read = booleans[1];
  18.  changed = booleans[2];
  19.  locked = booleans[3];
  20.  connected = booleans[4];
  21.  mail = booleans[5];
  22.  articleType = ArticleType.fromValue( parcel.readString() );
  23.  articleHeader = ArticleHeader.fromValue( parcel.readString() );
  24. }
  25.  

其中的 ArticleType.fromValue 是我慣用的列舉參數方式

詳細建構方式可以參考這個連結 Google 也愛用的列舉參數建構法

傳遞參數時則一樣使用 intent.putExtra

  1. intent.putExtra( "Article.Bean", articleBean );

取出參數則是使用 getParcelable 取出對應的值

  1. articleBean = getIntent().getExtras().getParcelable("Article.Bean");

以下是完整的 Class 程式碼範例

  1. public class ArticleBean implements Parcelable {
  2.  
  3.     private int serialNumber;
  4.  
  5.     private String aid;
  6.  
  7.     private String boardTitle;
  8.  
  9.     private String title;
  10.  
  11.     private String status;
  12.  
  13.     private String pushes;
  14.  
  15.     private String category;
  16.  
  17.     private String author;
  18.  
  19.     private String date;
  20.  
  21.     private boolean online;
  22.  
  23.     private boolean read;
  24.  
  25.     private boolean changed;
  26.  
  27.     private boolean locked;
  28.  
  29.     private boolean connected = false;
  30.  
  31.     private boolean mail = false;
  32.  
  33.     private ArticleType articleType;
  34.  
  35.     private ArticleHeader articleHeader;
  36.  
  37.     public int getSerialNumber() {
  38.         return serialNumber;
  39.     }
  40.  
  41.     public void setSerialNumber(int serialNumber) {
  42.         this.serialNumber = serialNumber;
  43.     }
  44.  
  45.     public String getAid() {
  46.         return aid;
  47.     }
  48.  
  49.     public void setAid(String aid) {
  50.         this.aid = aid;
  51.     }
  52.  
  53.     public String getBoardTitle() {
  54.         return boardTitle;
  55.     }
  56.  
  57.     public void setBoardTitle(String boardTitle) {
  58.         this.boardTitle = boardTitle;
  59.     }
  60.  
  61.     public String getTitle() {
  62.         return title;
  63.     }
  64.  
  65.     public void setTitle(String title) {
  66.         this.title = title;
  67.     }
  68.  
  69.     public String getStatus() {
  70.         return status;
  71.     }
  72.  
  73.     public void setStatus(String status) {
  74.         this.status = status;
  75.     }
  76.  
  77.     public String getPushes() {
  78.         return pushes;
  79.     }
  80.  
  81.     public void setPushes(String pushes) {
  82.         this.pushes = pushes;
  83.     }
  84.  
  85.     public String getCategory() {
  86.         return category;
  87.     }
  88.  
  89.     public void setCategory(String category) {
  90.         this.category = category;
  91.     }
  92.  
  93.     public String getAuthor() {
  94.         return author;
  95.     }
  96.  
  97.     public void setAuthor(String author) {
  98.         this.author = author;
  99.     }
  100.  
  101.     public String getDate() {
  102.         return date;
  103.     }
  104.  
  105.     public void setDate(String date) {
  106.         this.date = date;
  107.     }
  108.  
  109.     public boolean isOnline() {
  110.         return online;
  111.     }
  112.  
  113.     public void setOnline(boolean online) {
  114.         this.online = online;
  115.     }
  116.  
  117.     public boolean isRead() {
  118.         return read;
  119.     }
  120.  
  121.     public void setRead(boolean read) {
  122.         this.read = read;
  123.     }
  124.  
  125.     public boolean isChanged() {
  126.         return changed;
  127.     }
  128.  
  129.     public void setChanged(boolean changed) {
  130.         this.changed = changed;
  131.     }
  132.  
  133.     public boolean isLocked() {
  134.         return locked;
  135.     }
  136.  
  137.     public void setLocked(boolean locked) {
  138.         this.locked = locked;
  139.     }
  140.  
  141.     public boolean isConnected() {
  142.         return connected;
  143.     }
  144.  
  145.     public void setConnected(boolean connected) {
  146.         this.connected = connected;
  147.     }
  148.  
  149.     public boolean isMail() {
  150.         return mail;
  151.     }
  152.  
  153.     public void setMail(boolean mail) {
  154.         this.mail = mail;
  155.     }
  156.  
  157.     public ArticleType getArticleType() {
  158.         return articleType;
  159.     }
  160.  
  161.     public void setArticleType(ArticleType articleType) {
  162.         this.articleType = articleType;
  163.     }
  164.  
  165.     public ArticleHeader getArticleHeader() {
  166.         return articleHeader;
  167.     }
  168.  
  169.     public void setArticleHeader(ArticleHeader articleHeader) {
  170.         this.articleHeader = articleHeader;
  171.     }
  172.  
  173.     @Override
  174.     public int describeContents() {
  175.         return 0;
  176.     }
  177.  
  178.     @Override
  179.     public void writeToParcel(Parcel dest, int flags) {
  180.         dest.writeInt(serialNumber);
  181.         dest.writeString(boardTitle);
  182.         dest.writeString(aid);
  183.         dest.writeString(title);
  184.         dest.writeString(status);
  185.         dest.writeString(pushes);
  186.         dest.writeString(category);
  187.         dest.writeString(author);
  188.         dest.writeString(date);
  189.         dest.writeBooleanArray( new boolean[]{online, read, changed, locked, connected, mail} );
  190.         dest.writeString( articleType.getValue() );
  191.         dest.writeString(articleHeader.getValue());
  192.     }
  193.  
  194.     // 傳遞參數時 將會呼叫此方法重新創建物件
  195.     public static final Parcelable.Creator<ArticleBean> CREATOR = 
  196.      new Parcelable.Creator<ArticleBean>() {
  197.          public ArticleBean createFromParcel(Parcel parcel) {
  198.              return new ArticleBean(parcel);
  199.          }
  200.  
  201.          public ArticleBean[] newArray(int size) {
  202.              return new ArticleBean[size];
  203.          }
  204.      };
  205.  
  206.     private ArticleBean() {}
  207.  
  208.     // 以 Parcel 創建的建構子
  209.     private ArticleBean(Parcel parcel) {
  210.         boolean[] booleans = new boolean[6];
  211.  
  212.         // 所有參數皆須按照加入的順序取出
  213.         serialNumber = parcel.readInt();
  214.         boardTitle = parcel.readString();
  215.         aid = parcel.readString();
  216.         title = parcel.readString();
  217.         status = parcel.readString();
  218.         pushes = parcel.readString();
  219.         category = parcel.readString();
  220.         author = parcel.readString();
  221.         date = parcel.readString();
  222.  
  223.         parcel.readBooleanArray(booleans);
  224.  
  225.         online = booleans[0];
  226.         read = booleans[1];
  227.         changed = booleans[2];
  228.         locked = booleans[3];
  229.         connected = booleans[4];
  230.         mail = booleans[5];
  231.         articleType = ArticleType.fromValue( parcel.readString() );
  232.         articleHeader = ArticleHeader.fromValue( parcel.readString() );
  233.     }
  234.  
  235.     public static class Builder {
  236.         private int serialNumber;
  237.         private String aid;
  238.         private String boardTitle;
  239.         private String title;
  240.         private String status;
  241.         private String pushes;
  242.         private String category;
  243.         private String author;
  244.         private String date;
  245.         private boolean online;
  246.         private boolean read;
  247.         private boolean changed;
  248.         private boolean locked;
  249.         private boolean connected = false;
  250.         private boolean mail = false;
  251.         private ArticleType articleType;
  252.         private ArticleHeader articleHeader;
  253.  
  254.         private Builder() {
  255.         }
  256.  
  257.         public static Builder anArticleBean() {
  258.             return new Builder();
  259.         }
  260.  
  261.         public Builder withSerialNumber(int serialNumber) {
  262.             this.serialNumber = serialNumber;
  263.             return this;
  264.         }
  265.  
  266.         public Builder withAid(String aid) {
  267.             this.aid = aid;
  268.             return this;
  269.         }
  270.  
  271.         public Builder withBoardTitle(String boardTitle) {
  272.             this.boardTitle = boardTitle;
  273.             return this;
  274.         }
  275.  
  276.         public Builder withTitle(String title) {
  277.             this.title = title;
  278.             return this;
  279.         }
  280.  
  281.         public Builder withStatus(String status) {
  282.             this.status = status;
  283.             return this;
  284.         }
  285.  
  286.         public Builder withPushes(String pushes) {
  287.             this.pushes = pushes;
  288.             return this;
  289.         }
  290.  
  291.         public Builder withCategory(String category) {
  292.             this.category = category;
  293.             return this;
  294.         }
  295.  
  296.         public Builder withAuthor(String author) {
  297.             this.author = author;
  298.             return this;
  299.         }
  300.  
  301.         public Builder withDate(String date) {
  302.             this.date = date;
  303.             return this;
  304.         }
  305.  
  306.         public Builder withOnline(boolean online) {
  307.             this.online = online;
  308.             return this;
  309.         }
  310.  
  311.         public Builder withRead(boolean read) {
  312.             this.read = read;
  313.             return this;
  314.         }
  315.  
  316.         public Builder withChanged(boolean changed) {
  317.             this.changed = changed;
  318.             return this;
  319.         }
  320.  
  321.         public Builder withLocked(boolean locked) {
  322.             this.locked = locked;
  323.             return this;
  324.         }
  325.  
  326.         public Builder withConnected(boolean connected) {
  327.             this.connected = connected;
  328.             return this;
  329.         }
  330.  
  331.         public Builder withMail(boolean mail) {
  332.             this.mail = mail;
  333.             return this;
  334.         }
  335.  
  336.         public Builder withArticleType(ArticleType articleType) {
  337.             this.articleType = articleType;
  338.             return this;
  339.         }
  340.  
  341.         public Builder withArticleHeader(ArticleHeader articleHeader) {
  342.             this.articleHeader = articleHeader;
  343.             return this;
  344.         }
  345.  
  346.         public Builder but() {
  347.             return anArticleBean().withSerialNumber(serialNumber).withAid(aid).withBoardTitle(boardTitle).withTitle(title).withStatus(status).withPushes(pushes).withCategory(category).withAuthor(author).withDate(date).withOnline(online).withRead(read).withChanged(changed).withLocked(locked).withConnected(connected).withMail(mail).withArticleType(articleType).withArticleHeader(articleHeader);
  348.         }
  349.  
  350.         public ArticleBean build() {
  351.             ArticleBean articleBean = new ArticleBean();
  352.             articleBean.setSerialNumber(serialNumber);
  353.             articleBean.setAid(aid);
  354.             articleBean.setBoardTitle(boardTitle);
  355.             articleBean.setTitle(title);
  356.             articleBean.setStatus(status);
  357.             articleBean.setPushes(pushes);
  358.             articleBean.setCategory(category);
  359.             articleBean.setAuthor(author);
  360.             articleBean.setDate(date);
  361.             articleBean.setOnline(online);
  362.             articleBean.setRead(read);
  363.             articleBean.setChanged(changed);
  364.             articleBean.setLocked(locked);
  365.             articleBean.setConnected(connected);
  366.             articleBean.setMail(mail);
  367.             articleBean.setArticleType(articleType);
  368.             articleBean.setArticleHeader(articleHeader);
  369.             return articleBean;
  370.         }
  371.     }
  372. }
各項資料連結
Android Parcelable
Google 也愛用的列舉參數建構法
於
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