Android Open Source - geoar-app Plugin Context

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License

The source code is released under:

Apache License

Java Source Code

/**
 * Copyright 2012 52North Initiative for Geospatial Open Source Software GmbH
 */*from   w w w.ja  v a2  s .c  o m*/
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.n52.geoar.newdata;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import org.n52.geoar.GeoARApplication;
import org.n52.geoar.R;

import android.content.Context;
import android.content.ContextWrapper;
import android.content.res.AssetManager;
import android.content.res.Resources;
import android.content.res.Resources.Theme;
import android.os.Build;
import android.util.DisplayMetrics;
import android.view.LayoutInflater;
import android.view.WindowManager;

/**
 * A custom {@link Context} wrapping an existing Context, but returning a
 * special {@link Resources} instance reflecting the assets of a
 * {@link InstalledPluginHolder} as {@link Context#getResources()} return value.
 * 
 * Other relevant methods are overridden to return values reflecting a single
 * plugin instead of the wrapped Context.
 */
public class PluginContext extends ContextWrapper {
  private LayoutInflater mLayoutInflater;
  private Theme mTheme;
  private Resources mPluginResources;
  private InstalledPluginHolder mPlugin;

  /**
   * Constructs a {@link Resources} instance by creating an
   * {@link AssetManager} linked explicitly to this custom plugin using
   * reflection to access the non-code assets of this plugin without relying
   * on {@link Context#getResources()}, which is not available for manually
   * loaded application packages
   * 
   * @return
   */
  @Override
  public Resources getResources() {
    if (mPluginResources == null) {

      Constructor<AssetManager> constructor;
      try {
        // For unknown reasons, the AssetManager constructor is not
        // public
        constructor = AssetManager.class.getConstructor();
        constructor.setAccessible(true);
        AssetManager assetManager = constructor.newInstance();

        // For unknown reasons, the addAssetPath method is not public
        Method method = AssetManager.class.getMethod("addAssetPath",
            String.class);
        method.setAccessible(true);
        method.invoke(assetManager, mPlugin.getPluginFile()
            .getAbsolutePath());

        // get display metrics
        WindowManager windowManager = (WindowManager) GeoARApplication.applicationContext
            .getSystemService(Context.WINDOW_SERVICE);
        DisplayMetrics displayMetrics = new DisplayMetrics();
        windowManager.getDefaultDisplay().getMetrics(displayMetrics);

        // Create Resources object, no Configuration object required
        mPluginResources = new Resources(assetManager, displayMetrics,
            null);
      } catch (NoSuchMethodException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
      } catch (IllegalArgumentException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
      } catch (InstantiationException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
      } catch (IllegalAccessException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
      } catch (InvocationTargetException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
      }
    }

    return mPluginResources;
  }

  public PluginContext(Context base, InstalledPluginHolder plugin) {
    super(base);

    this.mPlugin = plugin;
  }

  @Override
  public Object getSystemService(String name) {
    if (LAYOUT_INFLATER_SERVICE.equals(name)) {
      if (mLayoutInflater == null) {
        // Get and store a LayoutInflater for this special
        // plugin context and do not use the cached inflater
        mLayoutInflater = LayoutInflater.from(getBaseContext())
            .cloneInContext(this);
      }
      return mLayoutInflater;
    }
    return super.getSystemService(name);
  }

  @Override
  public String getPackageResourcePath() {
    return mPlugin.getPluginFile().getAbsolutePath();
  }

  @Override
  public ClassLoader getClassLoader() {
    return mPlugin.getPluginClassLoader();
  }

  @Override
  public Theme getTheme() {
    if (mTheme == null) {
      // Create special theme to include the custom Resources
      // instance for a plugin
      mTheme = getResources().newTheme();
      // Previous approach, failed on devices with special device default
      // theme different to application theme
      // mTheme.setTo(getBaseContext().getTheme());

      // Now explicitly set Holo style (switch to ABS style when ABS
      // works) to allow to obtain all expected styled attributes
      mTheme.applyStyle(R.style.GeoAR_Theme, false);
      if (Build.VERSION.SDK_INT >= 11) {
        mTheme.applyStyle(android.R.style.Theme_Holo, false);
      } else {
        mTheme.applyStyle(android.R.style.Theme_Black, false);
      }
    }
    return mTheme;
  }

  @Override
  public String getPackageCodePath() {
    return mPlugin.getPluginFile().getAbsolutePath();
  }

}

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