从 Android Activity 获取上下文

Question

我已经使用一个显示图像缩略图的 GridView 和一个全屏 Activity 实现了一个图像库，它将以全屏模式显示每个图像。文件路径使用 Intents (putExtra) 传递给 GridView Activity，以根据 SDCARD 中的文件夹名称显示不同的 GridView。现在我遇到的问题是我无法将这些文件路径传递给 Fullscreen Activity 以便分别查看每个图像。

以下是我的课程；

MainActivity.java

package info.androidhive.imageslider;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {

    private Button btn1, btn2;
    Intent intent;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        btn1 = (Button) findViewById(R.id.button1);
        btn2 = (Button) findViewById(R.id.button2);
        setOnClickListeners();
    }

    public void setOnClickListeners(){
        btn1.setOnClickListener(this);
        btn2.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        switch(v.getId()){
        case R.id.button1:
            Toast.makeText(getApplicationContext(), "Loading Gridview 1", Toast.LENGTH_LONG).show();
            intent = new Intent(MainActivity.this, GridViewActivity.class);
            intent.putExtra("folder", "folder1");
            startActivity(intent);
            break;
        case R.id.button2:
            Toast.makeText(getApplicationContext(), "Loading Gridview 2", Toast.LENGTH_LONG).show();
            intent = new Intent(MainActivity.this, GridViewActivity.class);
            intent.putExtra("folder", "folder2");
            startActivity(intent);
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }



}

所以在这个活动中，每次点击按钮都会传递不同的文件夹名称。

GridViewActivity.java

此类将接收文件夹名称的意图参数，并将列出该特定文件夹的所有图像缩略图。直到这里一切都很好，我可以根据单击的按钮查看每个不同文件夹的图像。

package info.androidhive.imageslider;

import info.androidhive.imageslider.adapter.GridViewImageAdapter;
import info.androidhive.imageslider.helper.AppConstant;
import info.androidhive.imageslider.helper.Utils;

import java.io.File;
import java.util.ArrayList;
import java.util.Locale;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Point;
import android.os.Bundle;
import android.util.TypedValue;
import android.view.Display;
import android.view.WindowManager;
import android.widget.GridView;
import android.widget.Toast;

public class GridViewActivity extends Activity {

    private Utils utils;
    private ArrayList<String> imagePaths = new ArrayList<String>();
    private GridViewImageAdapter adapter;
    private GridView gridView;
    private int columnWidth;

    //Utils
    private Context mContext;




    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_grid_view);

        gridView = (GridView) findViewById(R.id.grid_view);



        //utils = new Utils(this);
        mContext = this;


        // Initilizing Grid View
        InitilizeGridLayout();

        // loading all image paths from SD card
        imagePaths = getFilePaths();

        // Gridview adapter
        adapter = new GridViewImageAdapter(GridViewActivity.this, imagePaths,
                columnWidth);

        // setting grid view adapter
        gridView.setAdapter(adapter);
    }



    private void InitilizeGridLayout() {
        Resources r = getResources();
        float padding = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,
                AppConstant.GRID_PADDING, r.getDisplayMetrics());

        columnWidth = (int) ((getScreenWidth() - ((AppConstant.NUM_OF_COLUMNS + 1) * padding)) / AppConstant.NUM_OF_COLUMNS);

        gridView.setNumColumns(AppConstant.NUM_OF_COLUMNS);
        gridView.setColumnWidth(columnWidth);
        gridView.setStretchMode(GridView.NO_STRETCH);
        gridView.setPadding((int) padding, (int) padding, (int) padding,
                (int) padding);
        gridView.setHorizontalSpacing((int) padding);
        gridView.setVerticalSpacing((int) padding);
    }

    /*
     * Reading file paths from SDCard // Utils
     */
    public ArrayList<String> getFilePaths() {
        ArrayList<String> filePaths = new ArrayList<String>();

        String folder = getIntent().getStringExtra("folder");

        File directory = new File(
                android.os.Environment.getExternalStorageDirectory()
                        + File.separator + folder);

        // check for directory
        if (directory.isDirectory()) {
            // getting list of file paths
            File[] listFiles = directory.listFiles();

            // Check for count
            if (listFiles.length > 0) {

                // loop through all files
                for (int i = 0; i < listFiles.length; i++) {

                    // get file path
                    String filePath = listFiles[i].getAbsolutePath();

                    // check for supported file extension
                    if (IsSupportedFile(filePath)) {
                        // Add image path to array list
                        filePaths.add(filePath);
                    }
                }
            } else {
                // image directory is empty
                Toast.makeText(
                        mContext,
                        folder
                                + " is empty. Please load some images in it !",
                        Toast.LENGTH_LONG).show();
            }

        } else {
            AlertDialog.Builder alert = new AlertDialog.Builder(mContext);
            alert.setTitle("Error!");
            alert.setMessage(folder
                    + " directory path is not valid! Please set the image directory name AppConstant.java class");
            alert.setPositiveButton("OK", null);
            alert.show();
        }

        return filePaths;
    }

    /*
     * Check supported file extensions
     * 
     * @returns boolean
     */
    private boolean IsSupportedFile(String filePath) {
        String ext = filePath.substring((filePath.lastIndexOf(".") + 1),
                filePath.length());

        if (AppConstant.FILE_EXTN
                .contains(ext.toLowerCase(Locale.getDefault())))
            return true;
        else
            return false;

    }

    /*
     * getting screen width
     */
    @SuppressLint("NewApi")
    public int getScreenWidth() {
        int columnWidth;
        WindowManager wm = (WindowManager) mContext
                .getSystemService(Context.WINDOW_SERVICE);
        Display display = wm.getDefaultDisplay();

        final Point point = new Point();
        try {
            display.getSize(point);
        } catch (java.lang.NoSuchMethodError ignore) { // Older device
            point.x = display.getWidth();
            point.y = display.getHeight();
        }
        columnWidth = point.x;
        return columnWidth;
    }


}

现在单击图像缩略图后，我的（FullScreenView 活动）无法获取文件夹名称，因此我可以在全屏模式下显示图像。

FullScreenViewActivity.java

package info.androidhive.imageslider;

import info.androidhive.imageslider.adapter.FullScreenImageAdapter;
//import info.androidhive.imageslider.helper.Utils;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.view.ViewPager;

public class FullScreenViewActivity extends Activity{

    private GridViewActivity gv;
    private FullScreenImageAdapter adapter;
    private ViewPager viewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fullscreen_view);

        viewPager = (ViewPager) findViewById(R.id.pager);

        //utils = new GridViewActivity(getApplicationContext());

        Intent i = getIntent();
        int position = i.getIntExtra("position", 0);

        adapter = new FullScreenImageAdapter(FullScreenViewActivity.this,
                gv.getFilePaths());

        viewPager.setAdapter(adapter);

        // displaying selected image first
        viewPager.setCurrentItem(position);
    }
}

我想知道如何在我的 FullScreenActivity 中接收文件参数？

Answer 1

你可以使用

intent.putStringArrayListExtra("paths", getFilePaths());

当您从 GridViewActivity 转到 FullScreenViewActivity 并在 onCreate 或 FullScreenViewActivity 中时，您可以这样做

ArrayList<String> paths = getIntent().getStringArrayListExtra("paths");

这将为您提供图像的路径