这是15的“建立一个社交媒体应用程序在Android工作室”教程中的一部分，我们将要在本文中介绍了以下功能：
- 我们将删除ChatActivity中的消息。
- 我们将删除文本和图像消息。当我们单击文本时，将出现一个AlertBox 。
- 有两个选项可以删除该消息或取消该事件。单击删除后，消息将从两侧被删除。
分步实施
步骤1：使用AdapterChat。 Java文件
仅当我们是邮件的发件人时，我们才能删除该邮件。有两种删除消息的方法。您可以使用其中任何一个。一方面，我们使用datasnapshot删除了该值，另一方面，我们将消息更新为“此消息已删除”，如我们在WhatsApp中看到的那样。
if(dataSnapshot1.child("sender").getValue().equals(myuid)) {
// any two of below can be used
dataSnapshot1.getRef().removeValue();
// <----------------------------------->
HashMap hashMap = new HashMap<>();
hashMap.put("message", "This Message Was Deleted");
dataSnapshot1.getRef().updateChildren(hashMap);
Toast.makeText(context,"Message Deleted.....",Toast.LENGTH_LONG).show();
} 下面是AdapterChat的代码。 Java文件。
Java
package com.example.socialmediaapp;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.text.format.DateFormat;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import com.bumptech.glide.Glide;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.Query;
import com.google.firebase.database.ValueEventListener;
import java.util.Calendar;
import java.util.List;
import java.util.Locale;
import de.hdodenhof.circleimageview.CircleImageView;
public class AdapterChat extends RecyclerView.Adapter {
private static final int MSG_TYPE_LEFT = 0;
private static final int MSG_TYPR_RIGHT = 1;
Context context;
List list;
String imageurl;
FirebaseUser firebaseUser;
public AdapterChat(Context context, List list, String imageurl) {
this.context = context;
this.list = list;
this.imageurl = imageurl;
}
@NonNull
@Override
public Myholder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
if (viewType == MSG_TYPE_LEFT) {
View view = LayoutInflater.from(context).inflate(R.layout.row_chat_left, parent, false);
return new Myholder(view);
} else {
View view = LayoutInflater.from(context).inflate(R.layout.row_chat_right, parent, false);
return new Myholder(view);
}
}
@Override
public void onBindViewHolder(@NonNull Myholder holder, final int position) {
String message = list.get(position).getMessage();
String timeStamp = list.get(position).getTimestamp();
String type = list.get(position).getType();
Calendar calendar = Calendar.getInstance(Locale.ENGLISH);
calendar.setTimeInMillis(Long.parseLong(timeStamp));
String timedate = DateFormat.format("dd/MM/yyyy hh:mm aa", calendar).toString();
holder.message.setText(message);
holder.time.setText(timedate);
try {
Glide.with(context).load(imageurl).into(holder.image);
} catch (Exception e) {
}
if (type.equals("text")) {
holder.message.setVisibility(View.VISIBLE);
holder.mimage.setVisibility(View.GONE);
holder.message.setText(message);
} else {
holder.message.setVisibility(View.GONE);
holder.mimage.setVisibility(View.VISIBLE);
Glide.with(context).load(message).into(holder.mimage);
}
holder.msglayput.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
AlertDialog.Builder builder = new AlertDialog.Builder(context);
builder.setTitle("Delete Message");
builder.setMessage("Are You Sure To Delete This Messgae");
builder.setPositiveButton("Delete", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
deleteMsg(position);
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
builder.create().show();
}
});
}
private void deleteMsg(int position) {
final String myuid = FirebaseAuth.getInstance().getCurrentUser().getUid();
String msgtimestmp = list.get(position).getTimestamp();
DatabaseReference dbref = FirebaseDatabase.getInstance().getReference().child("Chats");
Query query = dbref.orderByChild("timestamp").equalTo(msgtimestmp);
query.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
if (dataSnapshot1.child("sender").getValue().equals(myuid)) {
// any two of below can be used
dataSnapshot1.getRef().removeValue();
/* HashMap hashMap = new HashMap<>();
hashMap.put("message", "This Message Was Deleted");
dataSnapshot1.getRef().updateChildren(hashMap);
Toast.makeText(context,"Message Deleted.....",Toast.LENGTH_LONG).show();
*/
} else {
Toast.makeText(context, "you can delet only your msg....", Toast.LENGTH_LONG).show();
}
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
@Override
public int getItemCount() {
return list.size();
}
@Override
public int getItemViewType(int position) {
firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
if (list.get(position).getSender().equals(firebaseUser.getUid())) {
return MSG_TYPR_RIGHT;
} else {
return MSG_TYPE_LEFT;
}
}
class Myholder extends RecyclerView.ViewHolder {
CircleImageView image;
ImageView mimage;
TextView message, time, isSee;
LinearLayout msglayput;
public Myholder(@NonNull View itemView) {
super(itemView);
image = itemView.findViewById(R.id.profilec);
message = itemView.findViewById(R.id.msgc);
time = itemView.findViewById(R.id.timetv);
isSee = itemView.findViewById(R.id.isSeen);
msglayput = itemView.findViewById(R.id.msglayout);
mimage = itemView.findViewById(R.id.images);
}
}
} 输出：
对于本文中使用的所有可绘制文件，请参考以下链接： https://drive.google.com/drive/folders/1M_knOH_ugCuwSP5nkYzeD4dRp-Honzbe?usp=sharing
下面是执行这些操作后的文件结构：
