Android:Intent传递数据的几种类型和源码实现

public class Intent implements Parcelable, Cloneable {   //... private String mAction;
    private Uri mData;
    private String mType;
    private String mPackage;
    private ComponentName mComponent;
    private int mFlags;
    private HashSet<String> mCategories;
    private Bundle mExtras;
    private Rect mSourceBounds;

转自：http://blog.csdn.net/annkie/article/details/8483253

Intent也是继承了Parcelable的接口。

 

个人理解，Intent应该只是一个数据参数的载体，真正将两个Acitivity/Service通信起来的是Binder接口(C/S架构)。

 

第一类:简单或基本数据类型

Intent putExtra(String name, int[] value)
Intent putExtra(String name, float value)
Intent putExtra(String name, byte[] value)
Intent putExtra(String name, long[] value)
Intent putExtra(String name, float[] value)
Intent putExtra(String name, long value)
Intent putExtra(String name, String[] value)
Intent putExtra(String name, boolean value)
Intent putExtra(String name, boolean[] value)
Intent putExtra(String name, short value)
Intent putExtra(String name, double value)
Intent putExtra(String name, short[] value)
Intent putExtra(String name, String value)
Intent putExtra(String name, byte value)
Intent putExtra(String name, char[] value)
Intent putExtra(String name, CharSequence[] value)

本质上仍然是通过一个Bundle(private Bundle mExtras;)来实现：

 

public Intent putExtra(String name, long value) {
     if (mExtras == null) {
         mExtras = new Bundle();
     }
     mExtras.putLong(name, value);
     return this;
 }

 

 

 第二类:传递一个Bundle

public Intent putExtra(String name, Bundle value) {
        if (mExtras == null) {
            mExtras = new Bundle();
        }
        mExtras.putBundle(name, value);
        return this;
    }

 

 第三类：传递Serializable对象

public Intent putExtra(String name, Serializable value) {
        if (mExtras == null) {
            mExtras = new Bundle();
        }
        mExtras.putSerializable(name, value);
        return this;
    }

 

 第四类：Parcelable对象

public Intent putExtra(String name, Parcelable value) {
        if (mExtras == null) {
            mExtras = new Bundle();
        }
        mExtras.putParcelable(name, value);
        return this;
}
public Intent putExtra(String name, Parcelable[] value) {
        if (mExtras == null) {
            mExtras = new Bundle();
        }
        mExtras.putParcelableArray(name, value);
        return this;
    }

 

第五类：Intent

public Intent putExtras(Intent src) {
       if (src.mExtras != null) {
           if (mExtras == null) {
               mExtras = new Bundle(src.mExtras);
           } else {
               mExtras.putAll(src.mExtras);
           }
       }
       return this;
   }

归根结底都是通过Bundle来实现数据封装。而Bundle则是通过Map的数据结构来存储数据。

mMap = new HashMap<String, Object>();

mParcelledData

两者同时只有一个有效。

一旦unparcel以后，mParcelledData

的数据将被填充到mMap中，同时值为null。在writeToParcel和readFromParcel中则直接使用mParcelledData.此时一般通过IBinder关联两个进程的通信。

 

关于Bundle则是实现了Parcelable接口的类，通过上面提到的HashMap和一个Parcel来存储数据。

 

public final class Bundle implements Parcelable, Cloneable {
    private static final String LOG_TAG = "Bundle";
    public static final Bundle EMPTY;

    static {
        EMPTY = new Bundle();
        EMPTY.mMap = Collections.unmodifiableMap(new HashMap<String, Object>());
    }

    // Invariant - exactly one of mMap / mParcelledData will be null
    // (except inside a call to unparcel)

    /* package */ Map<String, Object> mMap = null;

    /*
     * If mParcelledData is non-null, then mMap will be null and the
     * data are stored as a Parcel containing a Bundle.  When the data
     * are unparcelled, mParcelledData willbe set to null.
     */
    /* package */ Parcel mParcelledData = null;

 

 public void putFloat(String key, float value) {
        unparcel();//首先解析出mParcelledData到mMap
        mMap.put(key, value);
    }


/* package */ synchronized void unparcel() {
        if (mParcelledData == null) {
            return;
        }

        int N = mParcelledData.readInt();
        if (N < 0) {
            return;
        }
        if (mMap == null) {
            mMap = new HashMap<String, Object>();
        }
        mParcelledData.readMapInternal(mMap, N, mClassLoader);
        mParcelledData.recycle();
        mParcelledData = null;//回收以后值为null
    }