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Diffstat (limited to 'core/java/android/view/ViewHierarchyEncoder.java')
| -rw-r--r-- | core/java/android/view/ViewHierarchyEncoder.java | 201 |
1 files changed, 201 insertions, 0 deletions
diff --git a/core/java/android/view/ViewHierarchyEncoder.java b/core/java/android/view/ViewHierarchyEncoder.java new file mode 100644 index 0000000..8770216 --- /dev/null +++ b/core/java/android/view/ViewHierarchyEncoder.java @@ -0,0 +1,201 @@ +package android.view; + +import android.annotation.NonNull; +import android.annotation.Nullable; + +import java.io.ByteArrayOutputStream; +import java.io.DataOutputStream; +import java.io.IOException; +import java.nio.charset.Charset; +import java.util.HashMap; +import java.util.Map; + +/** + * {@link ViewHierarchyEncoder} is a serializer that is tailored towards writing out + * view hierarchies (the view tree, along with the properties for each view) to a stream. + * + * It is typically used as follows: + * <pre> + * ViewHierarchyEncoder e = new ViewHierarchyEncoder(); + * + * for (View view : views) { + * e.beginObject(view); + * e.addProperty("prop1", value); + * ... + * e.endObject(); + * } + * + * // repeat above snippet for each view, finally end with: + * e.endStream(); + * </pre> + * + * <p>On the stream, a snippet such as the above gets encoded as a series of Map's (one + * corresponding to each view) with the property name as the key and the property value + * as the value. + * + * <p>Since the property names are practically the same across all views, rather than using + * the property name directly as the key, we use a short integer id corresponding to each + * property name as the key. A final map is added at the end which contains the mapping + * from the integer to its property name. + * + * <p>A value is encoded as a single byte type identifier followed by the encoding of the + * value. Only primitive types are supported as values, in addition to the Map type. + * + * @hide + */ +public class ViewHierarchyEncoder { + // Prefixes for simple primitives. These match the JNI definitions. + private static final byte SIG_BOOLEAN = 'Z'; + private static final byte SIG_BYTE = 'B'; + private static final byte SIG_SHORT = 'S'; + private static final byte SIG_INT = 'I'; + private static final byte SIG_LONG = 'J'; + private static final byte SIG_FLOAT = 'F'; + private static final byte SIG_DOUBLE = 'D'; + + // Prefixes for some commonly used objects + private static final byte SIG_STRING = 'R'; + + private static final byte SIG_MAP = 'M'; // a map with an short key + private static final short SIG_END_MAP = 0; + + private final DataOutputStream mStream; + + private final Map<String,Short> mPropertyNames = new HashMap<String, Short>(200); + private short mPropertyId = 1; + private Charset mCharset = Charset.forName("utf-8"); + + public ViewHierarchyEncoder(@NonNull ByteArrayOutputStream stream) { + mStream = new DataOutputStream(stream); + } + + public void beginObject(@NonNull Object o) { + startPropertyMap(); + addProperty("meta:__name__", o.getClass().getName()); + addProperty("meta:__hash__", o.hashCode()); + } + + public void endObject() { + endPropertyMap(); + } + + public void endStream() { + // write out the string table + startPropertyMap(); + addProperty("__name__", "propertyIndex"); + for (Map.Entry<String,Short> entry : mPropertyNames.entrySet()) { + writeShort(entry.getValue()); + writeString(entry.getKey()); + } + endPropertyMap(); + } + + public void addProperty(@NonNull String name, boolean v) { + writeShort(createPropertyIndex(name)); + writeBoolean(v); + } + + public void addProperty(@NonNull String name, short s) { + writeShort(createPropertyIndex(name)); + writeShort(s); + } + + public void addProperty(@NonNull String name, int v) { + writeShort(createPropertyIndex(name)); + writeInt(v); + } + + public void addProperty(@NonNull String name, float v) { + writeShort(createPropertyIndex(name)); + writeFloat(v); + } + + public void addProperty(@NonNull String name, @Nullable String s) { + writeShort(createPropertyIndex(name)); + writeString(s); + } + + /** + * Writes the given name as the property name, and leaves it to the callee + * to fill in value for this property. + */ + public void addPropertyKey(@NonNull String name) { + writeShort(createPropertyIndex(name)); + } + + private short createPropertyIndex(@NonNull String name) { + Short index = mPropertyNames.get(name); + if (index == null) { + index = mPropertyId++; + mPropertyNames.put(name, index); + } + + return index; + } + + private void startPropertyMap() { + try { + mStream.write(SIG_MAP); + } catch (IOException e) { + // does not happen since the stream simply wraps a ByteArrayOutputStream + } + } + + private void endPropertyMap() { + writeShort(SIG_END_MAP); + } + + private void writeBoolean(boolean v) { + try { + mStream.write(SIG_BOOLEAN); + mStream.write(v ? 1 : 0); + } catch (IOException e) { + // does not happen since the stream simply wraps a ByteArrayOutputStream + } + } + + private void writeShort(short s) { + try { + mStream.write(SIG_SHORT); + mStream.writeShort(s); + } catch (IOException e) { + // does not happen since the stream simply wraps a ByteArrayOutputStream + } + } + + private void writeInt(int i) { + try { + mStream.write(SIG_INT); + mStream.writeInt(i); + } catch (IOException e) { + // does not happen since the stream simply wraps a ByteArrayOutputStream + } + } + + private void writeFloat(float v) { + try { + mStream.write(SIG_FLOAT); + mStream.writeFloat(v); + } catch (IOException e) { + // does not happen since the stream simply wraps a ByteArrayOutputStream + } + } + + private void writeString(@Nullable String s) { + if (s == null) { + s = ""; + } + + try { + mStream.write(SIG_STRING); + byte[] bytes = s.getBytes(mCharset); + + short len = (short)Math.min(bytes.length, Short.MAX_VALUE); + mStream.writeShort(len); + + mStream.write(bytes, 0, len); + } catch (IOException e) { + // does not happen since the stream simply wraps a ByteArrayOutputStream + } + } +} |