Android:Intent傳遞數據的幾種類型和源碼實現

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;

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

Intent也是繼承了Parcelable的接口。

 

個人理解，Intent應該只是一個數據參數的載體，真正將兩個Acitivity/Service通信起來的是Binder接口(C/S架構)。

 

第一類:簡單或基本數據類型

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)

本質上仍然是通過一個Bundle(private Bundle mExtras;)來實現：

 

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

 

 

 第二類:傳遞一個Bundle

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

 

 第三類：傳遞Serializable對象

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

 

 第四類：Parcelable對象

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;
    }

 

第五類：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;
   }

歸根結底都是通過Bundle來實現數據封裝。而Bundle則是通過Map的數據結構來存儲數據。

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

mParcelledData

兩者同時只有一個有效。

一旦unparcel以后，mParcelledData

的數據將被填充到mMap中，同時值為null。在writeToParcel和readFromParcel中則直接使用mParcelledData.此時一般通過IBinder關聯兩個進程的通信。

 

關於Bundle則是實現了Parcelable接口的類，通過上面提到的HashMap和一個Parcel來存儲數據。

 

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;//回收以后值為null
    }